Angle difference between two bearings: Difference between revisions
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=={{header|Haskell}}== |
=={{header|Haskell}}== |
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<lang Haskell>import |
<lang Haskell>import Control.Monad (join) |
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import Data.Bifunctor (bimap) |
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import Text.Printf (printf) |
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type Radians = Float |
type Radians = Float |
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type Degrees = Float |
type Degrees = Float |
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---------- ANGLE DIFFERENCE BETWEEN TWO BEARINGS --------- |
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= |
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where |
where |
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(ax, ay) = (sin a, cos a) |
(ax, ay) = (sin a, cos a) |
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| otherwise = -1 |
| otherwise = -1 |
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main :: IO () |
main :: IO () |
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main = |
main = |
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putStrLn . unlines $ |
putStrLn . unlines $ |
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fmap |
fmap |
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(uncurry |
( uncurry (printf "%6.2f° + %6.2f° -> %7.2f°") |
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<*> angleBetweenDegrees |
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) |
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[ (20.0, 45.0), |
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(-45.0, 45.0), |
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(-85.0, 90.0), |
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(-95.0, 90.0), |
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(-45.0, 125.0), |
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(-45.0, 145.0) |
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]</lang> |
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] |
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------------------------- GENERIC ------------------------ |
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{{Out}} |
{{Out}} |
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<pre> 20.00° + 45.00° -> 25.00° |
<pre> 20.00° + 45.00° -> 25.00° |
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Revision as of 09:19, 23 May 2021
You are encouraged to solve this task according to the task description, using any language you may know.
Finding the angle between two bearings is often confusing.[1]
- Task
Find the angle which is the result of the subtraction b2 - b1, where b1 and b2 are the bearings.
Input bearings are expressed in the range -180 to +180 degrees.
The result is also expressed in the range -180 to +180 degrees.
Compute the angle for the following pairs:
- 20 degrees (b1) and 45 degrees (b2)
- -45 and 45
- -85 and 90
- -95 and 90
- -45 and 125
- -45 and 145
- 29.4803 and -88.6381
- -78.3251 and -159.036
- Optional extra
Allow the input bearings to be any (finite) value.
- Test cases
- -70099.74233810938 and 29840.67437876723
- -165313.6666297357 and 33693.9894517456
- 1174.8380510598456 and -154146.66490124757
- 60175.77306795546 and 42213.07192354373
11l
<lang 11l>F get_difference(b1, b2)
R wrap(b2 - b1, -180.0, 180.0)
print(get_difference( 20.0, 45.0)) print(get_difference(-45.0, 45.0)) print(get_difference(-85.0, 90.0)) print(get_difference(-95.0, 90.0)) print(get_difference(-45.0, 125.0)) print(get_difference(-45.0, 145.0)) print(get_difference(-45.0, 125.0)) print(get_difference(-45.0, 145.0)) print(get_difference(29.4803, -88.6381)) print(get_difference(-78.3251, -159.036)) print(‘’) print(get_difference(-70099.74233810938, 29840.67437876723)) print(get_difference(-165313.6666297357, 33693.9894517456)) print(get_difference(1174.8380510598456, -154146.66490124757)) print(get_difference(60175.77306795546, 42213.07192354373))</lang>
- Output:
25 90 175 -175 170 -170 170 -170 -118.118 -80.7109 -139.583 -72.3439 -161.503 37.2989
360 Assembly
<lang 360asm>* Angle difference between two bearings - 06/06/2018 ANGLEDBB CSECT
USING ANGLEDBB,R13 base register
B 72(R15) skip savearea
DC 17F'0' savearea
SAVE (14,12) save previous context
ST R13,4(R15) link backward
ST R15,8(R13) link forward
LR R13,R15 set addressability
LA R10,T-4 @t
LA R6,1 i=1
DO WHILE=(C,R6,LE,N) do i=1 to n
LA R10,4(R10) next @t
L R7,0(R10) a=t(i,1)
LA R10,4(R10) next @t
L R8,0(R10) b=t(i,2)
LR R4,R8 b
SR R4,R7 b-a
SRDA R4,32 ~
D R4,=F'3600000' /360
A R4,=F'5400000' +540
SRDA R4,32 ~
D R4,=F'3600000' /360
S R4,=F'1800000' x=((((b-a)//360)+540)//360)-180
XDECO R7,XDEC edit a
MVC PG(8),XDEC output a
MVC PG+9(4),XDEC+8 output a decimals
XDECO R8,XDEC edit b
MVC PG+14(8),XDEC output b
MVC PG+23(4),XDEC+8 output b decimals
XDECO R4,XDEC edit x
MVC PG+28(8),XDEC output x
MVC PG+37(4),XDEC+8 output x decimals
XPRNT PG,L'PG print
LA R6,1(R6) i++
ENDDO , enddo i
L R13,4(0,R13) restore previous savearea pointer
RETURN (14,12),RC=0 restore registers from calling sav
N DC F'8' number of pairs T DC F'200000',F'450000',F'-450000',F'450000'
DC F'-850000',F'900000',F'-950000',F'900000'
DC F'-450000',F'1250000',F'450000',F'1450000'
DC F'294803',F'-886361',F'-783251',F'-1590360'
PG DC CL80'12345678.1234 12345678.1234 12345678.1234' XDEC DS CL12 temp
YREGS
END ANGLEDBB</lang>
- Output:
20.0000 45.0000 25.0000
-45.0000 45.0000 90.0000
-85.0000 90.0000 175.0000
-95.0000 90.0000 -175.0000
-45.0000 125.0000 170.0000
45.0000 145.0000 100.0000
29.4803 -88.6361 -118.1164
-78.3251 -159.0360 -80.7109
Ada
Ada does not provide a built-in mod function for floating point types. This program supplies one. <lang Ada>
-- Angle difference between two bearings
with Ada.Text_IO; use Ada.Text_IO;
procedure Bearing_Angles is
type Real is digits 8;
Package Real_Io is new Ada.Text_IO.Float_IO(Real);
use Real_IO;
type Angles is record
B1 : Real;
B2 : Real;
end record;
type Angle_Arr is array(Positive range <>) of Angles;
function fmod(Left, Right : Real) return Real is
Result : Real;
begin
Result := Left - Right*Real'Truncation(Left / Right);
return Result;
end fmod;
The_Angles : Angle_Arr := ((20.0,45.0),(-45.0, 45.0), (-85.0, 90.0),
(-95.0, 90.0), (-14.0, 125.0), (29.4803, -88.6381),
(-78.3251, -159.036),
(-70099.74233810938, 29840.67437876723),
(-165313.6666297357, 33693.9894517456),
(1174.8380510598456, -154146.66490124757),
(60175.77306795546, 42213.07192354373));
Diff : Real;
begin
for A of The_Angles loop
Diff := fmod(A.b2 - A.b1, 360.0);
If Diff < -180.0 then
Diff := Diff + 360.0;
elsif Diff > 180.0 then
Diff := Diff - 360.0;
end if;
Put("Difference between ");
Put(Item => A.B2, Fore => 7, Aft => 4, Exp => 0);
Put(" and ");
Put(Item => A.B1, Fore => 7, Aft => 4, Exp => 0);
Put(" is ");
Put(Item => Diff, Fore => 4, Aft => 4, Exp => 0);
New_Line;
end loop;
end Bearing_Angles; </lang>
- Output:
Difference between 45.0000 and 20.0000 is 25.0000 Difference between 45.0000 and -45.0000 is 90.0000 Difference between 90.0000 and -85.0000 is 175.0000 Difference between 90.0000 and -95.0000 is -175.0000 Difference between 125.0000 and -14.0000 is 139.0000 Difference between -88.6381 and 29.4803 is -118.1184 Difference between -159.0360 and -78.3251 is -80.7109 Difference between 29840.6744 and -70099.7423 is -139.5833 Difference between 33693.9895 and -165313.6666 is -72.3439 Difference between -154146.6649 and 1174.8381 is -161.5030 Difference between 42213.0719 and 60175.7731 is 37.2989
APL
Returns an angle in (-180,180]; so two opposite bearings have a difference of 180 degrees, which is more natural than -180 degrees. <lang APL>[0] D←B1 DIFF B2 [1] D←180+¯360|180+B2-B1 </lang>
- Output:
'B1' 'B2' 'DIFFERENCE'⍪(⊂'¯¯¯¯¯¯¯¯¯¯')⍪(⊃B),DIFF/¨B
B1 B2 DIFFERENCE
¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯
20 45 25
¯45 45 90
¯85 90 175
¯95 90 ¯175
¯45 125 170
¯45 145 ¯170
29.48 ¯88.64 ¯118.12
¯78.33 ¯159.04 ¯80.71
¯70099.74 29840.67 ¯139.59
¯165313.67 3369.99 ¯156.34
1174.84 ¯154146.66 ¯161.5
60175.77 42213.07 37.3
270 DIFF 90.01
¯179.99
270 DIFF 90
180
AWK
<lang AWK>
- syntax: GAWK -f ANGLE_DIFFERENCE_BETWEEN_TWO_BEARINGS.AWK
BEGIN {
fmt = "%11s %11s %11s\n"
while (++i <= 11) { u = u "-" }
printf(fmt,"B1","B2","DIFFERENCE")
printf(fmt,u,u,u)
main(20,45)
main(-45,45)
main(-85,90)
main(-95,90)
main(-45,125)
main(-45,145)
main(29.4803,-88.6381)
main(-78.3251,-159.036)
main(-70099.74233810938,29840.67437876723)
main(-165313.6666297357,33693.9894517456)
main(1174.8380510598456,-154146.66490124757)
main(60175.77306795546,42213.07192354373)
exit(0)
} function main(b1,b2) {
printf("%11.2f %11.2f %11.2f\n",b1,b2,angle_difference(b1,b2))
} function angle_difference(b1,b2, r) {
r = (b2 - b1) % 360
if (r < -180) {
r += 360
}
if (r >= 180) {
r -= 360
}
return(r)
} </lang>
- Output:
B1 B2 DIFFERENCE
----------- ----------- -----------
20.00 45.00 25.00
-45.00 45.00 90.00
-85.00 90.00 175.00
-95.00 90.00 -175.00
-45.00 125.00 170.00
-45.00 145.00 -170.00
29.48 -88.64 -118.12
-78.33 -159.04 -80.71
-70099.74 29840.67 -139.58
-165313.67 33693.99 -72.34
1174.84 -154146.66 -161.50
60175.77 42213.07 37.30
Befunge
<lang befunge>012pv1 2 3 4 5 6 7 8
>&:v >859**%:459**1-`#v_ >12g!:12p#v_\-:459**1-`#v_ >.>
>0`#^_8v >859**-^ >859**-^
^:+**95< > ^
</lang> The labelled points are: 1. Initialise write/not write and read input, 2. Put in the range 0-360 if negative, 3. Likewise if positive, 4. Put in range -180 - 180, 5. Check if write/not write step, 6. If write find difference, 7. Scale to -180 - 180, 8. Write out and onto next pair.
Unfortunately, due to the lack of floating-point arithmetic in befunge, it is impossible to do the full challenge, however, given the integer truncations of these values it works.
Input:
20 45 -45 45 -85 90 -95 90 -45 125 -45 145 29 -88 -78 -159 -70099 29840 -165313 33693 1174 -154146 60175 42213
- Output:
25 90 175 -175 170 -170 -117 -81 -141 -74 -160 38
C
This implementation either reads two bearings from the console or a file containing a list of bearings. Usage printed on incorrect invocation. <lang C>
- include<stdlib.h>
- include<stdio.h>
- include<math.h>
void processFile(char* name){
int i,records; double diff,b1,b2; FILE* fp = fopen(name,"r");
fscanf(fp,"%d\n",&records);
for(i=0;i<records;i++){ fscanf(fp,"%lf%lf",&b1,&b2);
diff = fmod(b2-b1,360.0); printf("\nDifference between b2(%lf) and b1(%lf) is %lf",b2,b1,(diff<-180)?diff+360:((diff>=180)?diff-360:diff)); }
fclose(fp); }
int main(int argC,char* argV[]) { double diff;
if(argC < 2) printf("Usage : %s <bearings separated by a space OR full file name which contains the bearing list>",argV[0]); else if(argC == 2) processFile(argV[1]); else{ diff = fmod(atof(argV[2])-atof(argV[1]),360.0); printf("Difference between b2(%s) and b1(%s) is %lf",argV[2],argV[1],(diff<-180)?diff+360:((diff>=180)?diff-360:diff)); }
return 0; } </lang> Invocation and output for two bearings :
C:\rosettaCode>bearingDiff.exe 29.4803 -88.6381 Difference between b2(-88.6381) and b1(29.4803) is -118.118400
File format for bearing list :
<Number of records> <Each record consisting of two bearings separated by a space>
Input file :
12 20 45 -45 45 -85 90 -95 90 -45 125 -45 145 29.4803 -88.6381 -78.3251 -159.036 -70099.74233810938 29840.67437876723 -165313.6666297357 33693.9894517456 1174.8380510598456 -154146.66490124757 60175.77306795546 42213.07192354373
Invocation and output for above bearing list file :
C:\rosettaCode>bearingDiff.exe bearingList.txt Difference between b2(45.000000) and b1(20.000000) is 25.000000 Difference between b2(45.000000) and b1(-45.000000) is 90.000000 Difference between b2(90.000000) and b1(-85.000000) is 175.000000 Difference between b2(90.000000) and b1(-95.000000) is -175.000000 Difference between b2(125.000000) and b1(-45.000000) is 170.000000 Difference between b2(145.000000) and b1(-45.000000) is -170.000000 Difference between b2(-88.638100) and b1(29.480300) is -118.118400 Difference between b2(-159.036000) and b1(-78.325100) is -80.710900 Difference between b2(29840.674379) and b1(-70099.742338) is -139.583283 Difference between b2(33693.989452) and b1(-165313.666630) is -72.343919 Difference between b2(-154146.664901) and b1(1174.838051) is -161.502952 Difference between b2(42213.071924) and b1(60175.773068) is 37.298856
C#
<lang csharp>using System;
namespace Angle_difference_between_two_bearings { class Program { public static void Main(string[] args) { Console.WriteLine(); Console.WriteLine("Hello World!"); Console.WriteLine();
// Calculate standard test cases Console.WriteLine(Delta_Bearing( 20M,45)); Console.WriteLine(Delta_Bearing(-45M,45M)); Console.WriteLine(Delta_Bearing(-85M,90M)); Console.WriteLine(Delta_Bearing(-95M,90M)); Console.WriteLine(Delta_Bearing(-45M,125M)); Console.WriteLine(Delta_Bearing(-45M,145M)); Console.WriteLine(Delta_Bearing( 29.4803M,-88.6381M)); Console.WriteLine(Delta_Bearing(-78.3251M, -159.036M));
// Calculate optional test cases Console.WriteLine(Delta_Bearing(-70099.74233810938M, 29840.67437876723M)); Console.WriteLine(Delta_Bearing(-165313.6666297357M, 33693.9894517456M)); Console.WriteLine(Delta_Bearing( 1174.8380510598456M, -154146.66490124757M)); Console.WriteLine(Delta_Bearing( 60175.77306795546M, 42213.07192354373M));
Console.WriteLine(); Console.Write("Press any key to continue . . . "); Console.ReadKey(true); }
static decimal Delta_Bearing(decimal b1, decimal b2) { /* * Optimal solution * decimal d = 0;
d = (b2-b1)%360;
if(d>180) d -= 360; else if(d<-180) d += 360;
return d; * * */
//
//
//
decimal d = 0;
// Convert bearing to W.C.B if(b1<0) b1 += 360; if(b2<0) b2 += 360;
///Calculate delta bearing //and //Convert result value to Q.B. d = (b2 - b1)%360;
if(d>180) d -= 360; else if(d<-180) d += 360;
return d;
// // // } } }</lang>
- Output:
Hello World! 25 90 175 -175 170 -170 -118,1184 -80,7109 -139,58328312339 -72,3439185187 -161,5029523074156 37,29885558827 Press any key to continue . . .
C++
<lang cpp>#include <cmath>
- include <iostream>
using namespace std;
double getDifference(double b1, double b2) { double r = fmod(b2 - b1, 360.0); if (r < -180.0) r += 360.0; if (r >= 180.0) r -= 360.0; return r; }
int main() { cout << "Input in -180 to +180 range" << endl; cout << getDifference(20.0, 45.0) << endl; cout << getDifference(-45.0, 45.0) << endl; cout << getDifference(-85.0, 90.0) << endl; cout << getDifference(-95.0, 90.0) << endl; cout << getDifference(-45.0, 125.0) << endl; cout << getDifference(-45.0, 145.0) << endl; cout << getDifference(-45.0, 125.0) << endl; cout << getDifference(-45.0, 145.0) << endl; cout << getDifference(29.4803, -88.6381) << endl; cout << getDifference(-78.3251, -159.036) << endl;
cout << "Input in wider range" << endl; cout << getDifference(-70099.74233810938, 29840.67437876723) << endl; cout << getDifference(-165313.6666297357, 33693.9894517456) << endl; cout << getDifference(1174.8380510598456, -154146.66490124757) << endl; cout << getDifference(60175.77306795546, 42213.07192354373) << endl;
return 0; }</lang>
- Output:
Input in -180 to +180 range 25 90 175 -175 170 -170 170 -170 -118.118 -80.7109 Input in wider range -139.583 -72.3439 -161.503 37.2989
Clojure
<lang clojure>(defn angle-difference [a b]
(let [r (mod (- b a) 360)]
(if (>= r 180)
(- r 360)
r)))
(angle-difference 20 45) ; 25 (angle-difference -45 45) ; 90 (angle-difference -85 90) ; 175 (angle-difference -95 90) ; -175 (angle-difference -70099.74 29840.67) ; -139.59 </lang>
COBOL
<lang cobol>
******************************************************************
* COBOL solution to Angle difference challange
* The program was run on OpenCobolIDE
* I chose to read the input data from a .txt file that I
* created on my PC rather than to hard code it into the
* program or enter it as the program was executing.
******************************************************************
IDENTIFICATION DIVISION.
PROGRAM-ID. ANGLE-DIFFERENCE.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT IN-FILE ASSIGN TO 'C:\Both\Rosetta\Angle_diff.txt'
ORGANIZATION IS LINE SEQUENTIAL.
DATA DIVISION.
FILE SECTION.
FD IN-FILE.
01 IN-RECORD.
05 ALPHA-BEARING-1 PIC X(20).
05 FILLER PIC X.
05 ALPHA-BEARING-2 PIC X(20).
WORKING-STORAGE SECTION.
01 SWITCHES.
05 EOF-SWITCH PIC X VALUE 'N'.
01 COUNTERS.
05 REC-CTR PIC 9(3) VALUE 0.
01 WS-ALPHA-BEARING.
05 WS-AB-SIGN PIC X.
88 WS-AB-NEGATIVE VALUE "-".
05 WS-AB-INTEGER-PART PIC X(6).
05 WS-AB-DEC-POINT PIC X.
05 WS-AB-DECIMAL-PART PIC X(12).
01 WS-BEARING-1 PIC S9(6)V9(12).
01 WS-BEARING-2 PIC S9(6)V9(12).
01 WS-BEARING PIC S9(6)V9(12).
01 FILLER REDEFINES WS-BEARING.
05 WSB-INTEGER-PART PIC X(6).
05 WSB-DECIMAL-PART PIC X9(12).
77 WS-RESULT PIC S9(6)V9(12).
77 WS-RESULT-POS PIC 9(6)V9(12).
77 WS-INTEGER-PART PIC 9(6).
77 WS-DECIMAL-PART PIC V9(12).
77 WS-RESULT-OUT PIC ------9.9999.
PROCEDURE DIVISION.
000-MAIN.
PERFORM 100-INITIALIZE.
PERFORM 200-PROCESS-RECORD
UNTIL EOF-SWITCH = 'Y'.
PERFORM 300-TERMINATE.
STOP RUN.
100-INITIALIZE.
OPEN INPUT IN-FILE.
PERFORM 150-READ-RECORD.
150-READ-RECORD.
READ IN-FILE
AT END
MOVE 'Y' TO EOF-SWITCH
NOT AT END
COMPUTE REC-CTR = REC-CTR + 1
END-READ.
200-PROCESS-RECORD.
MOVE ALPHA-BEARING-1 TO WS-ALPHA-BEARING.
PERFORM 250-CONVERT-DATA.
MOVE WS-BEARING TO WS-BEARING-1.
MOVE ALPHA-BEARING-2 TO WS-ALPHA-BEARING.
PERFORM 250-CONVERT-DATA.
MOVE WS-BEARING TO WS-BEARING-2.
COMPUTE WS-RESULT = WS-BEARING-2 - WS-BEARING-1.
MOVE WS-RESULT TO WS-RESULT-POS.
MOVE WS-RESULT-POS TO WS-INTEGER-PART.
COMPUTE WS-DECIMAL-PART = WS-RESULT-POS - WS-INTEGER-PART.
COMPUTE WS-INTEGER-PART = FUNCTION MOD(WS-INTEGER-PART 360).
IF WS-RESULT > 0
COMPUTE WS-RESULT = WS-INTEGER-PART + WS-DECIMAL-PART
ELSE
COMPUTE WS-RESULT =
(WS-INTEGER-PART + WS-DECIMAL-PART) * -1
END-IF.
IF WS-RESULT < -180
COMPUTE WS-RESULT = WS-RESULT + 360.
IF WS-RESULT > 180
COMPUTE WS-RESULT = WS-RESULT - 360.
COMPUTE WS-RESULT-OUT ROUNDED = WS-RESULT.
DISPLAY REC-CTR ' ' WS-RESULT-OUT.
PERFORM 150-READ-RECORD.
250-CONVERT-DATA.
MOVE WS-AB-INTEGER-PART TO WSB-INTEGER-PART.
MOVE WS-AB-DECIMAL-PART TO WSB-DECIMAL-PART.
IF WS-AB-NEGATIVE
SUBTRACT WS-BEARING FROM ZERO
GIVING WS-BEARING
END-IF.
300-TERMINATE.
DISPLAY 'RECORDS PROCESSED: ' REC-CTR.
CLOSE IN-FILE.
******************************************************************
* INPUT FILE ('Angle_diff.txt' stored on my PC at:
* 'C:\Both\Rosetta\Angle_diff.txt'
******************************************************************
* +000020.000000000000 +000045.000000000000
* -000045.000000000000 +000045.000000000000
* -000085.000000000000 +000090.000000000000
* -000095.000000000000 +000090.000000000000
* -000045.000000000000 +000125.000000000000
* -000045.000000000000 +000145.000000000000
* +000029.480300000000 -000088.638100000000
* -000078.325100000000 -000159.036000000000
* -070099.742338109380 +029840.674378767230
* -165313.666629735700 +033693.989451745600
* +001174.838051059846 -154146.664901247570
* +060175.773067955460 +042213.071923543730
******************************************************************
* OUTPUT:
******************************************************************
* 001 25.0000
* 002 90.0000
* 003 175.0000
* 004 -175.0000
* 005 170.0000
* 006 -170.0000
* 007 -118.1184
* 008 -80.7109
* 009 -139.5833
* 010 -72.3439
* 011 -161.5030
* 012 37.2989
******************************************************************
</lang>
Common Lisp
<lang common lisp> (defun angle-difference (b1 b2) (let ((diff (mod (- b2 b1) 360))) (if (< diff -180) (incf diff 360) (if (> diff 180) (decf diff 360) diff)))) </lang>
- Output:
CL-USER> (angle-difference 20 45) 25 CL-USER> (angle-difference -45 45) 90 CL-USER> (angle-difference -85 90) 175 CL-USER> (angle-difference -95 90) -175 CL-USER> (angle-difference -70099.74 29840.67) -139.58594
D
<lang D>import std.stdio;
double getDifference(double b1, double b2) {
double r = (b2 - b1) % 360.0;
if (r < -180.0) {
r += 360.0;
}
if (r >= 180.0) {
r -= 360.0;
}
return r;
}
void main() {
writeln("Input in -180 to +180 range");
writeln(getDifference(20.0, 45.0));
writeln(getDifference(-45.0, 45.0));
writeln(getDifference(-85.0, 90.0));
writeln(getDifference(-95.0, 90.0));
writeln(getDifference(-45.0, 125.0));
writeln(getDifference(-45.0, 145.0));
writeln(getDifference(-45.0, 125.0));
writeln(getDifference(-45.0, 145.0));
writeln(getDifference(29.4803, -88.6381));
writeln(getDifference(-78.3251, -159.036));
writeln("Input in wider range");
writeln(getDifference(-70099.74233810938, 29840.67437876723));
writeln(getDifference(-165313.6666297357, 33693.9894517456));
writeln(getDifference(1174.8380510598456, -154146.66490124757));
writeln(getDifference(60175.77306795546, 42213.07192354373));
}</lang>
- Output:
Input in -180 to +180 range 25 90 175 -175 170 -170 170 -170 -118.118 -80.7109 Input in wider range -139.583 -72.3439 -161.503 37.2989
Delphi
See #Pascal.
Erlang
The real number calculations are done using integer arithmetic to better handle rounding errors. Erlang uses extended precision integers so there will be no overflow. The module is tested by running the test function, which in turn matches expected results with the result of function call. <lang Erlang> -module(bearings).
%% API -export([angle_sub_degrees/2,test/0]).
-define(RealAngleMultiplier,16#10000000000). -define(DegreesPerTurn,360). -define(Precision,9). %%%=================================================================== %%% API %%%===================================================================
%%-------------------------------------------------------------------- %% @doc %% @spec %% @end %%-------------------------------------------------------------------- %% angle_sub_degrees(B1,B2) when is_integer(B1), is_integer(B2) ->
angle_sub(B2-B1,?DegreesPerTurn);
angle_sub_degrees(B1,B2) ->
NewB1 = trunc(B1*?RealAngleMultiplier), NewB2 = trunc(B2*?RealAngleMultiplier), round(angle_sub(NewB2 - NewB1,
?DegreesPerTurn*?RealAngleMultiplier) /?RealAngleMultiplier,?Precision).
%%%=================================================================== %%% Internal functions %%%===================================================================
%% delta normalises the angle difference. Consider a turn from 350 degrees %% to 20 degrees. Subtraction results in 330 degress. This is equivalent of %% a turn in the other direction of 30 degrees, thus 330 degrees is equal %% to -30 degrees.
angle_sub(Value,TurnSize) ->
NormalisedValue = Value rem TurnSize, minimise_angle(NormalisedValue,TurnSize).
% X rem Turn result in 0..Turn for X > 0 and -Turn..0 for X < 0 % specification requires -Turn/2 < X < Turn/2. This is achieved % by adding or removing a turn as required. % bsr 1 divides an integer by 2 minimise_angle(Angle,Turn) when Angle + (Turn bsr 1) < 0 ->
Angle+Turn;
minimise_angle(Angle,Turn) when Angle - (Turn bsr 1) > 0 ->
Angle-Turn;
minimise_angle(Angle,_) ->
Angle.
round(Number,Precision) ->
P = math:pow(10,Precision), round(Number*P)/P.
test() ->
25 = angle_sub_degrees(20,45), 90 = angle_sub_degrees(-45,45), 175 = angle_sub_degrees(-85,90), -175 = angle_sub_degrees(-95,90), 170 = angle_sub_degrees(-45,125), -170 = angle_sub_degrees(-45,145), -118.1184 = angle_sub_degrees( 29.4803,-88.6381), -139.583283124=angle_sub_degrees(-70099.742338109,29840.674378767), -72.343918514=angle_sub_degrees( -165313.66662974,33693.989451746), -161.50295231=angle_sub_degrees( 1174.8380510598,-154146.66490125), 37.298855589=angle_sub_degrees( 60175.773067955,42213.071923544),
passed.
</lang>
F#
<lang fsharp>let deltaBearing (b1:double) (b2:double) =
let r = (b2 - b1) % 360.0;
if r > 180.0 then
r - 360.0
elif r < -180.0 then
r + 360.0
else
r
[<EntryPoint>] let main _ =
printfn "%A" (deltaBearing 20.0 45.0) printfn "%A" (deltaBearing -45.0 45.0) printfn "%A" (deltaBearing -85.0 90.0) printfn "%A" (deltaBearing -95.0 90.0) printfn "%A" (deltaBearing -45.0 125.0) printfn "%A" (deltaBearing -45.0 145.0) printfn "%A" (deltaBearing 29.4803 -88.6381) printfn "%A" (deltaBearing -78.3251 -159.036) printfn "%A" (deltaBearing -70099.74233810938 29840.67437876723) printfn "%A" (deltaBearing -165313.6666297357 33693.9894517456) printfn "%A" (deltaBearing 1174.8380510598456 -154146.66490124757) printfn "%A" (deltaBearing 60175.77306795546 42213.07192354373) 0 // return an integer exit code</lang>
- Output:
25.0 90.0 175.0 -175.0 170.0 -170.0 -118.1184 -80.7109 -139.5832831 -72.34391852 -161.5029523 37.29885559
Factor
<lang factor>USING: combinators generalizations kernel math prettyprint ; IN: rosetta-code.bearings
- delta-bearing ( x y -- z )
swap - 360 mod {
{ [ dup 180 > ] [ 360 - ] }
{ [ dup -180 < ] [ 360 + ] }
[ ]
} cond ;
- bearings-demo ( -- )
20 45 -45 45 -85 90 -95 90 -45 125 -45 145 29.4803 -88.6381 -78.3251 -159.036 -70099.74233810938 29840.67437876723 -165313.6666297357 33693.9894517456 1174.8380510598456 -154146.66490124757 60175.77306795546 42213.07192354373 [ delta-bearing . ] 2 12 mnapply ;
MAIN: bearings-demo</lang>
- Output:
25 90 175 -175 170 -170 -118.1184 -80.7109 -139.5832831233856 -72.34391851868713 -161.5029523074045 37.29885558826936
Fortran
Rather than calculate angle differences and mess about with folding the results into ±180 and getting the sign right, why not use some mathematics? These days, trigonometrical functions are calculated swiftly by specialised hardware (well, microcode), and with the availability of functions working in degrees, matters are eased further nor is precision lost in converting from degrees to radians. So, the first step is to convert a bearing into an (x,y) unit vector via function CIS(t) = cos(t) + i.sin(t), which will handle all the annoyance of bearings specified in values above 360. Then, using the dot product of the two vectors allows the cosine of the angle to be known, and the cross product determines the sign.
However, this relies on the unit vectors being accurately so, and their subsequent dot product not exceeding one in size: given the rounding of results with the limited precision actual floating-point arithmetic, there may be problems. Proving that a calculation will not suffer these on a specific computer is difficult, especially as the desire for such a result may mean that any apparent pretext leading to that belief will be seized upon. Because calculations on the IBM pc and similar computers are conducted with 80-bit floating-point arithmetic, rounding errors for 64-bit results are likely to be small, but past experience leads to a "fog of fear" about the precise behaviour of floating-point arithmetic.
As it happens, the test data did not provoke any objections from the ACOSD function, but even so, a conversion to using arctan instead of arccos to recover angles would be safer. By using the four-quadrant arctan(x,y) function, the sign of the angle difference is also delivered and although that result could be in 0°-360° it turns out to be in ±180° as desired. On the other hand, the library of available functions did not include an arctan for complex parameters, so the complex number Z had to be split into its real and imaginary parts, thus requiring two appearances and to avoid repeated calculation, a temporary variable Z is needed. Otherwise, the statement could have been just T = ATAN2D(Z1*CONJG(Z2)) and the whole calculation could be effected in one statement, T = ATAN2D(CIS(90 - B1)*CONJG(CIS(90 - B2))) And, since cis(t) = exp(i.t), T = ATAN2D(EXP(CMPLX(0,90 - B1))*CONJG(EXP(CMPLX(0,90 - B2)))) - although using the arithmetic statement function does seem less intimidating.
The source style is F77 (even using the old-style arithmetic statement function) except for the convenience of generic functions taking the type of their parameters to save on the bother of DCMPLX instead of just CMPLX, etc. Floating-point constants in the test data are specified with ~D0, the exponential form that signifies double precision otherwise they would be taken as single precision values. Some compilers offer an option stating that all floating-point constants are to be taken as double precision. REAL*8 precision amounts to about sixteen decimal digits, so some of the supplied values will not be accurately represented, unless something beyond REAL*8 is available. <lang Fortran> SUBROUTINE BDIFF (B1,B2) !Difference B2 - B1, as bearings. All in degrees, not radians.
REAL*8 B1,B2 !Maximum precision, for large-angle folding.
COMPLEX*16 CIS,Z1,Z2,Z !Scratchpads.
CIS(T) = CMPLX(COSD(T),SIND(T)) !Convert an angle into a unit vector.
Z1 = CIS(90 - B1) !Bearings run clockwise from north (y) around to east (x).
Z2 = CIS(90 - B2) !Mathematics runs counterclockwise from x (east).
Z = Z1*CONJG(Z2) !(Z1x,Z1y)(Z2x,-Z2y) = (Z1x.Z2x + Z1y.Z2y, Z1y.Z2x - Z1x.Z2y)
T = ATAN2D(AIMAG(Z),REAL(Z)) !Madly, arctan(x,y) is ATAN(Y,X)!
WRITE (6,10) B1,Z1,B2,Z2,T !Two sets of numbers, and a result.
10 FORMAT (2(F14.4,"(",F9.6,",",F9.6,")"),F9.3) !Two lots, and a tail.
END SUBROUTINE BDIFF !Having functions in degrees saves some bother.
PROGRAM ORIENTED
REAL*8 B(24) !Just prepare a wad of values.
DATA B/20D0,45D0, -45D0,45D0, -85D0,90D0, -95D0,90D0, !As specified.
1 -45D0,125D0, -45D0,145D0, 29.4803D0,-88.6381D0,
2 -78.3251D0, -159.036D0,
3 -70099.74233810938D0, 29840.67437876723D0,
4 -165313.6666297357D0, 33693.9894517456D0,
5 1174.8380510598456D0, -154146.66490124757D0,
6 60175.77306795546D0, 42213.07192354373D0/
WRITE (6,1) ("B",I,"x","y", I = 1,2) !Or, one could just list them twice.
1 FORMAT (28X,"Bearing calculations, in degrees"//
* 2(A13,I1,"(",A9,",",A9,")"),A9) !Compare format 10, above.
DO I = 1,23,2 !Step through the pairs.
CALL BDIFF(B(I),B(I + 1))
END DO
END</lang>
The output shows the stages:
Bearing calculations, in degrees
B1( x, y) B2( x, y)
20.0000( 0.342020, 0.939693) 45.0000( 0.707107, 0.707107) 25.000
-45.0000(-0.707107, 0.707107) 45.0000( 0.707107, 0.707107) 90.000
-85.0000(-0.996195, 0.087156) 90.0000( 1.000000, 0.000000) 175.000
-95.0000(-0.996195,-0.087156) 90.0000( 1.000000, 0.000000) -175.000
-45.0000(-0.707107, 0.707107) 125.0000( 0.819152,-0.573576) 170.000
-45.0000(-0.707107, 0.707107) 145.0000( 0.573576,-0.819152) -170.000
29.4803( 0.492124, 0.870525) -88.6381(-0.999718, 0.023767) -118.118
-78.3251(-0.979312, 0.202358) -159.0360(-0.357781,-0.933805) -80.711
-70099.7423( 0.984016,-0.178078) 29840.6744(-0.633734, 0.773551) -139.584
-165313.6666(-0.959667, 0.281138) 33693.9895(-0.559023,-0.829152) -72.340
1174.8381( 0.996437,-0.084339) -154146.6649(-0.918252, 0.395996) -161.510
60175.7731( 0.826820, 0.562467) 42213.0719( 0.998565,-0.053561) 37.297
FreeBASIC
<lang freebasic>' version 28-01-2019 ' compile with: fbc -s console
- Include "string.bi"
Function frmt(num As Double) As String
Dim As String temp = Format(num, "#######.#############") Dim As Integer i = Len(temp) -1
If temp[i] = Asc(".") Then temp[i] = 32
If InStr(temp, ".") = 0 Then
Return Right(Space(10) + temp, 9) + Space(13)
End If
temp = Space(10) + temp + Space(13)
Return Mid(temp, InStr(temp, ".") -8, 22)
End Function
' ------=< MAIN >=------
Dim As Double b1, b2, bb1, bb2, diff
Print Print " b1 b2 difference" Print " -----------------------------------------------------------"
Do
Read b1, b2 If b1 = 0 And b2 = 0 Then Exit Do diff = b2 - b1 diff = diff - Int(diff / 360) * 360 If diff > 180 Then diff -= 360 Print frmt(b1); frmt(b2); frmt(diff)
Loop
Data 20,45, -45,45, -85,90 Data -95,90, -45,125, -45,145 Data 29.4803,-88.6381, -78.3251,-159.036 Data -70099.74233810938, 29840.67437876723 Data -165313.6666297357, 33693.9894517456 Data 1174.8380510598456, -154146.66490124757 Data 60175.77306795546, 42213.07192354373
' empty keyboard buffer While InKey <> "" : Wend Print : Print "hit any key to end program" Sleep End</lang>
- Output:
b1 b2 difference
-----------------------------------------------------------
20 45 25
-45 45 90
-85 90 175
-95 90 -175
-45 125 170
-45 145 -170
29.4803 -88.6381 -118.1184
-78.3251 -159.036 -80.7109
-70099.7423381093831 29840.6743787672312 -139.5832831233856
-165313.6666297357006 33693.9894517455978 -72.3439185186871
1174.8380510598461 -154146.6649012475973 -161.5029523074336
60175.7730679554588 42213.0719235437282 37.2988555882694
Go
Basic task solution:
One feature of this solution is that if you can rely on the input bearings being in the range -180 to 180, you don't have to use math.Mod. Another feature is the bearing type and method syntax. <lang go>package main
import "fmt"
type bearing float64
var testCases = []struct{ b1, b2 bearing }{
{20, 45},
{-45, 45},
{-85, 90},
{-95, 90},
{-45, 125},
{-45, 145},
{29.4803, -88.6381},
{-78.3251, -159.036},
}
func main() {
for _, tc := range testCases {
fmt.Println(tc.b2.Sub(tc.b1))
}
}
func (b2 bearing) Sub(b1 bearing) bearing {
switch d := b2 - b1; {
case d < -180:
return d + 360
case d > 180:
return d - 360
default:
return d
}
}</lang>
- Output:
25 90 175 -175 170 -170 -118.1184 -80.7109
Optional extra solution:
A feature here is that the function body is a one-liner sufficient for the task test cases. <lang go>package main
import (
"fmt" "math"
)
var testCases = []struct{ b1, b2 float64 }{
{20, 45},
{-45, 45},
{-85, 90},
{-95, 90},
{-45, 125},
{-45, 145},
{29.4803, -88.6381},
{-78.3251, -159.036},
{-70099.74233810938, 29840.67437876723},
{-165313.6666297357, 33693.9894517456},
{1174.8380510598456, -154146.66490124757},
{60175.77306795546, 42213.07192354373},
}
func main() {
for _, tc := range testCases {
fmt.Println(angleDifference(tc.b2, tc.b1))
}
}
func angleDifference(b2, b1 float64) float64 {
return math.Mod(math.Mod(b2-b1, 360)+360+180, 360) - 180
}</lang>
- Output:
25 90 175 -175 170 -170 -118.11840000000001 -80.71089999999998 -139.58328312338563 -72.34391851868713 -161.50295230740448 37.29885558826936
Groovy
Solution A:
<lang groovy>def angleDifferenceA(double b1, double b2) {
r = (b2 - b1) % 360.0
(r > 180.0 ? r - 360.0
: r <= -180.0 ? r + 360.0
: r)
}</lang>
Solution B:
In the spirit of the Fortran "Why branch when you can math?" solution, but without all the messy trigonometry.
<lang groovy>def angleDifferenceB(double b1, double b2) {
((b2 - b1) % 360.0 - 540.0) % 360.0 + 180.0
}</lang> NOTE: We could ADD 540 and SUBTRACT 180 instead (as did many others, notably 360_Assembly, NewLISP, Racket, and REXX). The difference is that my choice normalizes "about face" to +180° while the other (At least in Groovy and other C-derived languages) normalizes "about face" to -180°.
Test: <lang groovy>println " b1 b2 diff A diff B" [
[b1: 20, b2: 45 ], [b1: -45, b2: 45 ], [b1: -85, b2: 90 ], [b1: -95, b2: 90 ], [b1: -45, b2: 125 ], [b1: -45, b2: 145 ], [b1: 29.4803, b2: -88.6381 ], [b1: -78.3251, b2: -159.036 ], [b1: -70099.74233810938, b2: 29840.67437876723 ], [b1:-165313.6666297357, b2: 33693.9894517456 ], [b1: 1174.8380510598456, b2:-154146.66490124757 ], [b1: 60175.77306795546, b2: 42213.07192354373 ]
].each { bearings ->
def (b1,b2) = bearings.values().collect{ it as double }
printf ("%22.13f %22.13f %22.13f %22.13f\n", b1, b2, angleDifferenceA(b1, b2), angleDifferenceB(b1, b2))
}</lang>
Output:
b1 b2 diff A diff B
20.0000000000000 45.0000000000000 25.0000000000000 25.0000000000000
-45.0000000000000 45.0000000000000 90.0000000000000 90.0000000000000
-85.0000000000000 90.0000000000000 175.0000000000000 175.0000000000000
-95.0000000000000 90.0000000000000 -175.0000000000000 -175.0000000000000
-45.0000000000000 125.0000000000000 170.0000000000000 170.0000000000000
-45.0000000000000 145.0000000000000 -170.0000000000000 -170.0000000000000
29.4803000000000 -88.6381000000000 -118.1184000000000 -118.1184000000000
-78.3251000000000 -159.0360000000000 -80.7109000000000 -80.7109000000000
-70099.7423381093800 29840.6743787672300 -139.5832831233856 -139.5832831233856
-165313.6666297357000 33693.9894517456000 -72.3439185186871 -72.3439185186871
1174.8380510598456 -154146.6649012475700 -161.5029523074045 -161.5029523074045
60175.7730679554600 42213.0719235437300 37.2988555882694 37.2988555882694
Haskell
<lang Haskell>import Control.Monad (join) import Data.Bifunctor (bimap) import Text.Printf (printf)
type Radians = Float
type Degrees = Float
ANGLE DIFFERENCE BETWEEN TWO BEARINGS ---------
angleBetweenDegrees :: (Degrees, Degrees) -> Degrees angleBetweenDegrees = degrees . bearingDelta . join bimap radians
bearingDelta :: (Radians, Radians) -> Radians bearingDelta (a, b) -- sign * dot-product
=
sign * acos ((ax * bx) + (ay * by))
where
(ax, ay) = (sin a, cos a)
(bx, by) = (sin b, cos b)
sign
| ((ay * bx) - (by * ax)) > 0 = 1
| otherwise = -1
TEST -------------------------
main :: IO () main =
putStrLn . unlines $
fmap
( uncurry (printf "%6.2f° + %6.2f° -> %7.2f°")
<*> angleBetweenDegrees
)
[ (20.0, 45.0),
(-45.0, 45.0),
(-85.0, 90.0),
(-95.0, 90.0),
(-45.0, 125.0),
(-45.0, 145.0)
]
GENERIC ------------------------
degrees :: Radians -> Degrees degrees = (/ pi) . (180 *)
radians :: Degrees -> Radians radians = (/ 180) . (pi *)</lang>
- Output:
20.00° + 45.00° -> 25.00° -45.00° + 45.00° -> 90.00° -85.00° + 90.00° -> 175.00° -95.00° + 90.00° -> -175.00° -45.00° + 125.00° -> 170.00° -45.00° + 145.00° -> -170.00°
IS-BASIC
<lang IS-BASIC>100 INPUT PROMPT "1. angle: ":A1 110 INPUT PROMPT "2. angle: ":A2 120 LET B=MOD(A2-A1,360) 130 IF B>180 THEN LET B=B-360 140 IF B<-180 THEN LET B=B+360 150 PRINT "Difference: ";B</lang>
J
<lang j>relativeBearing=: (180 -~ 360 | 180 + -~)/"1</lang> <lang j>tests=: _99&".;._2 noun define 20 45 -45 45 -85 90 -95 90 -45 125 -45 145 29.4803 -88.6381 -78.3251 -159.036 -70099.74233810938 29840.67437876723 -165313.6666297357 33693.9894517456 1174.8380510598456 -154146.66490124757 60175.77306795546 42213.07192354373 )
tests ,. relativeBearing tests
20 45 25
_45 45 90
_85 90 175
_95 90 _175
_45 125 170
_45 145 _170
29.4803 _88.6381 _118.118
_78.3251 _159.036 _80.7109 _70099.7 29840.7 _139.583
_165314 33694 _72.3439 1174.84 _154147 _161.503 60175.8 42213.1 37.2989</lang>
Java
<lang java>public class AngleDifference {
public static double getDifference(double b1, double b2) {
double r = (b2 - b1) % 360.0;
if (r < -180.0)
r += 360.0;
if (r >= 180.0)
r -= 360.0;
return r;
}
public static void main(String[] args) {
System.out.println("Input in -180 to +180 range");
System.out.println(getDifference(20.0, 45.0));
System.out.println(getDifference(-45.0, 45.0));
System.out.println(getDifference(-85.0, 90.0));
System.out.println(getDifference(-95.0, 90.0));
System.out.println(getDifference(-45.0, 125.0));
System.out.println(getDifference(-45.0, 145.0));
System.out.println(getDifference(-45.0, 125.0));
System.out.println(getDifference(-45.0, 145.0));
System.out.println(getDifference(29.4803, -88.6381));
System.out.println(getDifference(-78.3251, -159.036));
System.out.println("Input in wider range");
System.out.println(getDifference(-70099.74233810938, 29840.67437876723));
System.out.println(getDifference(-165313.6666297357, 33693.9894517456));
System.out.println(getDifference(1174.8380510598456, -154146.66490124757));
System.out.println(getDifference(60175.77306795546, 42213.07192354373));
}
}</lang>
- Output:
Input in -180 to +180 range 25.0 90.0 175.0 -175.0 170.0 -170.0 170.0 -170.0 -118.1184 -80.7109 Input in wider range -139.58328312338563 -72.34391851868713 -161.50295230740448 37.29885558826936
JavaScript
ES5
This approach should be reliable but it is also very inefficient.
<lang javascript>function relativeBearing(b1Rad, b2Rad) { b1y = Math.cos(b1Rad); b1x = Math.sin(b1Rad); b2y = Math.cos(b2Rad); b2x = Math.sin(b2Rad); crossp = b1y * b2x - b2y * b1x; dotp = b1x * b2x + b1y * b2y; if(crossp > 0.) return Math.acos(dotp); return -Math.acos(dotp); }
function test() { var deg2rad = 3.14159265/180.0; var rad2deg = 180.0/3.14159265; return "Input in -180 to +180 range\n" +relativeBearing(20.0*deg2rad, 45.0*deg2rad)*rad2deg+"\n" +relativeBearing(-45.0*deg2rad, 45.0*deg2rad)*rad2deg+"\n" +relativeBearing(-85.0*deg2rad, 90.0*deg2rad)*rad2deg+"\n" +relativeBearing(-95.0*deg2rad, 90.0*deg2rad)*rad2deg+"\n" +relativeBearing(-45.0*deg2rad, 125.0*deg2rad)*rad2deg+"\n" +relativeBearing(-45.0*deg2rad, 145.0*deg2rad)*rad2deg+"\n"
+relativeBearing(29.4803*deg2rad, -88.6381*deg2rad)*rad2deg+"\n" +relativeBearing(-78.3251*deg2rad, -159.036*deg2rad)*rad2deg+"\n"
+ "Input in wider range\n" +relativeBearing(-70099.74233810938*deg2rad, 29840.67437876723*deg2rad)*rad2deg+"\n" +relativeBearing(-165313.6666297357*deg2rad, 33693.9894517456*deg2rad)*rad2deg+"\n" +relativeBearing(1174.8380510598456*deg2rad, -154146.66490124757*deg2rad)*rad2deg+"\n" +relativeBearing(60175.77306795546*deg2rad, 42213.07192354373*deg2rad)*rad2deg+"\n";
}</lang>
- Output:
Input in -180 to +180 range 25.000000000000004 90 174.99999999999997 -175.00000041135993 170.00000000000003 -170.00000041135996 -118.1184 -80.71089999999998 Input in wider range -139.5833974814558 -72.34414600076728 -161.50277501127033 37.2988761562732
ES6
<lang JavaScript>(() => {
// bearingDelta :: Radians -> Radians -> Radians
const bearingDelta = (ar, br) => {
const [ax, ay] = [sin(ar), cos(ar)], [bx, by] = [sin(br), cos(br)],
// Cross-product > 0 ?
sign = ((ay * bx) - (by * ax)) > 0 ? +1 : -1;
// Sign * dot-product
return sign * acos((ax * bx) + (ay * by));
};
// Pi, sin, cos, acos :: Function
const [Pi, sin, cos, acos] = ['PI', 'sin', 'cos', 'acos']
.map(k => Math[k]),
degRad = x => Pi * x / 180.0,
radDeg = x => 180.0 * x / Pi;
// TEST ------------------------------------------------------------------
// justifyRight :: Int -> Char -> Text -> Text
const justifyRight = (n, cFiller, strText) =>
n > strText.length ? (
(cFiller.repeat(n) + strText)
.slice(-n)
) : strText;
// showMap :: Degrees -> Degrees -> String
const showMap = (da, db) =>
justifyRight(6, ' ', `${da}° +`) +
justifyRight(11, ' ', ` ${db}° -> `) +
justifyRight(7, ' ', `${(radDeg(bearingDelta(degRad(da), degRad(db))))
.toPrecision(4)}°`);
return [
[20, 45],
[-45, 45],
[-85, 90],
[-95, 90],
[-45, 125],
[-45, 145]
].map(xy => showMap(...xy))
.join('\n');
})();</lang>
- Output:
20° + 45° -> 25.00° -45° + 45° -> 90.00° -85° + 90° -> 175.0° -95° + 90° -> -175.0° -45° + 125° -> 170.0° -45° + 145° -> -170.0°
Jsish
<lang javascript>/* Angle difference between bearings, in Jsish */ function angleDifference(bearing1:number, bearing2:number):number {
var angle = (bearing2 - bearing1) % 360; if (angle < -180) angle += 360; if (angle >= 180) angle -= 360; return angle;
}
if (Interp.conf('unitTest')) {
var dataSet = [[20, 45], [-45, 45], [-85, 90], [-95, 90], [-45, 125], [-45, 145],
[29.4803, -88.6381], [-78.3251, -159.036],
[-70099.74233810938, 29840.67437876723],
[-165313.6666297357, 33693.9894517456],
[1174.8380510598456, -154146.66490124757],
[60175.77306795546, 42213.07192354373]];
printf(" Bearing 1 Bearing 2 Difference\n");
for (var i = 0; i < dataSet.length; i++) {
printf("%17S° %17S° %17S°\n", dataSet[i][0], dataSet[i][1],
angleDifference(dataSet[i][0], dataSet[i][1])
);
}
}
/*
!EXPECTSTART!
Bearing 1 Bearing 2 Difference
20° 45° 25°
-45° 45° 90°
-85° 90° 175°
-95° 90° -175°
-45° 125° 170°
-45° 145° -170°
29.4803° -88.6381° -118.1184°
-78.3251° -159.036° -80.7109°
-70099.7423381094° 29840.6743787672° -139.583283123386° -165313.666629736° 33693.9894517456° -72.3439185186871°
1174.83805105985° -154146.664901248° -161.502952307404° 60175.7730679555° 42213.0719235437° 37.2988555882694°
!EXPECTEND!
- /</lang>
- Output:
prompt$ jsish -u angleDifference.jsi [PASS] angleDifference.jsi
Julia
<lang julia>using Printf
function angdiff(a, b)
r = (b - a) % 360.0
if r ≥ 180.0
r -= 360.0
end
return r
end
println("Input in -180 to +180 range:") for (a, b) in [(20.0, 45.0), (-45.0, 45.0), (-85.0, 90.0), (-95.0, 90.0), (-45.0, 125.0), (-45.0, 145.0),
(-45.0, 125.0), (-45.0, 145.0), (29.4803, -88.6381), (-78.3251, -159.036)]
@printf("% 6.1f - % 6.1f = % 6.1f\n", a, b, angdiff(a, b))
end
println("\nInput in wider range:") for (a, b) in [(-70099.74233810938, 29840.67437876723), (-165313.6666297357, 33693.9894517456),
(1174.8380510598456, -154146.66490124757), (60175.77306795546, 42213.07192354373)]
@printf("% 9.1f - % 9.1f = % 6.1f\n", a, b, angdiff(a, b))
end</lang>
- Output:
Input in -180 to +180 range: 20.0 - 45.0 = 25.0 -45.0 - 45.0 = 90.0 -85.0 - 90.0 = 175.0 -95.0 - 90.0 = -175.0 -45.0 - 125.0 = 170.0 -45.0 - 145.0 = -170.0 -45.0 - 125.0 = 170.0 -45.0 - 145.0 = -170.0 29.5 - -88.6 = -118.1 -78.3 - -159.0 = -80.7 Input in wider range: -70099.7 - 29840.7 = -139.6 -165313.7 - 33694.0 = -72.3 1174.8 - -154146.7 = -161.5 60175.8 - 42213.1 = -322.7
K
<lang K> / Angle difference between two angles / angledif.k
angdif: {[b1;b2]; :[(r:(b2-b1)!360.0)<-180.0;r+:360.0;r>180.0;r-:360.0];:r} </lang>
The output of a session is given below:
- Output:
K Console - Enter \ for help \l angledif angdif[20;45] 25.0 angdif[-45;45] 90.0 angdif[-85;90] 175.0 angdif[-95;90] -175.0 angdif[-45;125] 170.0 angdif[29.4803;-88.6381] -118.1184 angdif[-78.3251;-159.036] -80.7109 angdif[-70099.74233810938;29840.67437876723] -139.5833
Klingphix
<lang Klingphix>include ..\Utilitys.tlhy
- bearing sub 360 mod 540 add 360 mod 180 sub ;
20 45 bearing -45 45 bearing -85 90 bearing -95 90 bearing -45 125 bearing -45 145 bearing 29.4803 -88.6381 bearing -78.3251 -159.036 bearing -70099.74233810938 29840.67437876723 bearing -165313.6666297357 33693.9894517456 bearing 1174.8380510598456 -154146.66490124757 bearing 60175.77306795546 42213.07192354373 bearing
pstack
" " input</lang>
- Output:
(-25, -90, -175, 175, -170, 170, 118.118, 80.7109, 139.583, 72.3439, 161.503, -37.2989)
Kotlin
<lang scala>// version 1.1.2
class Angle(d: Double) {
val value = when {
d in -180.0 .. 180.0 -> d
d > 180.0 -> (d - 180.0) % 360.0 - 180.0
else -> (d + 180.0) % 360.0 + 180.0
}
operator fun minus(other: Angle) = Angle(this.value - other.value)
}
fun main(args: Array<String>) {
val anglePairs = arrayOf(
20.0 to 45.0,
-45.0 to 45.0,
-85.0 to 90.0,
-95.0 to 90.0,
-45.0 to 125.0,
-45.0 to 145.0,
29.4803 to -88.6381,
-78.3251 to -159.036,
-70099.74233810938 to 29840.67437876723,
-165313.6666297357 to 33693.9894517456,
1174.8380510598456 to -154146.66490124757,
60175.77306795546 to 42213.07192354373
)
println(" b1 b2 diff")
val f = "% 12.4f % 12.4f % 12.4f"
for (ap in anglePairs) {
val diff = Angle(ap.second) - Angle(ap.first)
println(f.format(ap.first, ap.second, diff.value))
}
}</lang>
- Output:
b1 b2 diff
20.0000 45.0000 25.0000
-45.0000 45.0000 90.0000
-85.0000 90.0000 175.0000
-95.0000 90.0000 -175.0000
-45.0000 125.0000 170.0000
-45.0000 145.0000 -170.0000
29.4803 -88.6381 -118.1184
-78.3251 -159.0360 -80.7109
-70099.7423 29840.6744 -139.5833
-165313.6666 33693.9895 -72.3439
1174.8381 -154146.6649 -161.5030
60175.7731 42213.0719 37.2989
Lua
Each bearing will be stored in an object that inherits methods to accomplish all parts of the task: accept a new number of degrees, automatically adjusting to the range [-180, 180]; construct new bearing objects; subtract another bearing from itself and return the difference; construct a list of new bearing objects given a list of arbitrary degree sizes; and format the number of degrees into a modest human-readable format. Bearings will be zero-initialized by default if no degree size is provided.
<lang lua>bearing = {degrees = 0} -- prototype object
function bearing:assign(angle) angle = tonumber(angle) or 0 while angle > 180 do angle = angle - 360 end while angle < -180 do angle = angle + 360 end self.degrees = angle end
function bearing:new(size) local child_object = {} setmetatable(child_object, {__index = self}) child_object:assign(size) return child_object end
function bearing:subtract(other) local difference = self.degrees - other.degrees return self:new(difference) end
function bearing:list(sizes) local bearings = {} for index, size in ipairs(sizes) do table.insert(bearings, self:new(size)) end return bearings end
function bearing:text() return string.format("%.4f deg", self.degrees) end
function main() local subtrahends = bearing:list{ 20, -45, -85, -95, -45, -45, 29.4803, -78.3251, -70099.74233810938, -165313.6666297357, 1174.8380510598456, 60175.77306795546 } local minuends = bearing:list{ 45, 45, 90, 90, 125, 145, -88.6381, -159.036, 29840.67437876723, 33693.9894517456, -154146.66490124757, 42213.07192354373 } for index = 1, #minuends do local b2, b1 = minuends[index], subtrahends[index] local b3 = b2:subtract(b1) local statement = string.format( "%s - %s = %s\n", b2:text(), b1:text(), b3:text() ) io.write(statement) end end
main()</lang>
- Output:
45.0000 deg - 20.0000 deg = 25.0000 deg 45.0000 deg - -45.0000 deg = 90.0000 deg 90.0000 deg - -85.0000 deg = 175.0000 deg 90.0000 deg - -95.0000 deg = -175.0000 deg 125.0000 deg - -45.0000 deg = 170.0000 deg 145.0000 deg - -45.0000 deg = -170.0000 deg -88.6381 deg - 29.4803 deg = -118.1184 deg -159.0360 deg - -78.3251 deg = -80.7109 deg -39.3256 deg - 100.2577 deg = -139.5833 deg -146.0105 deg - -73.6666 deg = -72.3439 deg -66.6649 deg - 94.8381 deg = -161.5030 deg 93.0719 deg - 55.7731 deg = 37.2989 deg
Maple
<lang Maple>getDiff := proc(b1,b2) local r: r := frem(b2 - b1, 360): if r >= 180 then r := r - 360: fi: return r: end proc: getDiff(20,45); getDiff(-45,45); getDiff(-85,90); getDiff(-95,90); getDiff(-45,125); getDiff(-45,145); getDiff(29.4803, -88.6381); getDiff(-78.3251,-159.036); getDiff(-70099.74233810938,29840.67437876723); getDiff(-165313.6666297357,33693.9894517456); getDiff(1174.8380510598456,-154146.66490124757); getDiff(60175.77306795546,42213.07192354373)</lang>
- Output:
25 90 175 -175 170 -170 -118.1184 -80.7109 -139.58328 -72.3340 -161.5030 37.29885
Modula-2
<lang modula2>FROM Terminal IMPORT *;
PROCEDURE WriteRealLn(value : REAL); VAR str : ARRAY[0..16] OF CHAR; BEGIN
RealToStr(value, str); WriteString(str); WriteLn;
END WriteRealLn;
PROCEDURE AngleDifference(b1, b2 : REAL) : REAL; VAR r : REAL; BEGIN
r := (b2 - b1);
WHILE r < -180.0 DO
r := r + 360.0;
END;
WHILE r >= 180.0 DO
r := r - 360.0;
END;
RETURN r;
END AngleDifference;
BEGIN
WriteString('Input in -180 to +180 range');
WriteLn;
WriteRealLn(AngleDifference(20.0, 45.0));
WriteRealLn(AngleDifference(-45.0, 45.0));
WriteRealLn(AngleDifference(-85.0, 90.0));
WriteRealLn(AngleDifference(-95.0, 90.0));
WriteRealLn(AngleDifference(-45.0, 125.0));
WriteRealLn(AngleDifference(-45.0, 145.0));
WriteRealLn(AngleDifference(29.4803, -88.6381));
WriteRealLn(AngleDifference(-78.3251, -159.036));
WriteString('Input in wider range');
WriteLn;
WriteRealLn(AngleDifference(-70099.74233810938, 29840.67437876723));
WriteRealLn(AngleDifference(-165313.6666297357, 33693.9894517456));
WriteRealLn(AngleDifference(1174.8380510598456, -154146.66490124757));
WriteRealLn(AngleDifference(60175.77306795546, 42213.07192354373));
ReadChar;
END Bearings.</lang>
NewLISP
Taken from Racket solution
<lang lisp>
- !/usr/bin/env newlisp
(define (bearing- bearing heading) (sub (mod (add (mod (sub bearing heading) 360.0) 540.0) 360.0) 180.0))
(bearing- 20 45) (bearing- -45 45) (bearing- -85 90) (bearing- -95 90) (bearing- -45 125) (bearing- -45 145) (bearing- 29.4803 -88.6381) (bearing- -78.3251 -159.036) (bearing- -70099.74233810938 29840.67437876723) (bearing- -165313.6666297357 33693.9894517456) (bearing- 1174.8380510598456 -154146.66490124757) (bearing- 60175.77306795546 42213.07192354373)) </lang>
- Output:
-25 -90 -175 175 -170 170 118.11839999999995 80.71090000000004 139.58328312338563 72.34391851868713 161.50295230740448 -37.29885558826936
Nim
<lang nim>import math import strutils
proc delta(b1, b2: float) : float =
result = (b2 - b1) mod 360.0
if result < -180.0: result += 360.0 elif result >= 180.0: result -= 360.0
let testVectors : seq[tuple[b1, b2: float]] = @[
(20.00, 45.00 ),
(-45.00, 45.00 ),
(-85.00, 90.00 ),
(-95.00, 90.00 ),
(-45.00, 125.00 ),
(-45.00, 145.00 ),
( 29.48, -88.64 ),
(-78.33, -159.04 ),
(-70099.74, 29840.67 ),
(-165313.67, 33693.99 ),
(1174.84, -154146.66 ),
(60175.77, 42213.07 ) ]
for vector in testVectors:
echo vector.b1.formatFloat(ffDecimal, 2).align(13) &
vector.b2.formatFloat(ffDecimal, 2).align(13) &
delta(vector.b1, vector.b2).formatFloat(ffDecimal, 2).align(13)
</lang>
- Output:
20.00 45.00 25.00
-45.00 45.00 90.00
-85.00 90.00 175.00
-95.00 90.00 -175.00
-45.00 125.00 170.00
-45.00 145.00 -170.00
29.48 -88.64 -118.12
-78.33 -159.04 -80.71
-70099.74 29840.67 -139.59
-165313.67 33693.99 -72.34
1174.84 -154146.66 -161.50
60175.77 42213.07 37.30
OCaml
<lang ocaml>let get_diff b1 b2 =
let r = mod_float (b2 -. b1) 360.0 in if r < -180.0 then r +. 360.0 else if r >= 180.0 then r -. 360.0 else r
let () =
print_endline "Input in -180 to +180 range"; Printf.printf " %g\n" (get_diff 20.0 45.0); Printf.printf " %g\n" (get_diff (-45.0) 45.0); Printf.printf " %g\n" (get_diff (-85.0) 90.0); Printf.printf " %g\n" (get_diff (-95.0) 90.0); Printf.printf " %g\n" (get_diff (-45.0) 125.0); Printf.printf " %g\n" (get_diff (-45.0) 145.0); Printf.printf " %g\n" (get_diff (-45.0) 125.0); Printf.printf " %g\n" (get_diff (-45.0) 145.0); Printf.printf " %g\n" (get_diff 29.4803 (-88.6381)); Printf.printf " %g\n" (get_diff (-78.3251) (-159.036)); print_endline "Input in wider range"; Printf.printf " %g\n" (get_diff (-70099.74233810938) 29840.67437876723); Printf.printf " %g\n" (get_diff (-165313.6666297357) 33693.9894517456); Printf.printf " %g\n" (get_diff 1174.8380510598456 (-154146.66490124757)); Printf.printf " %g\n" (get_diff 60175.77306795546 42213.07192354373);
- </lang>
- Output:
Input in -180 to +180 range 25 90 175 -175 170 -170 170 -170 -118.118 -80.7109 Input in wider range -139.583 -72.3439 -161.503 37.2989
PARI/GP
<lang parigp>centerliftmod1(x)=frac(x+1/2)-1/2; anglediff(x,y)=centerliftmod1((y-x)/360)*360; vecFunc(f)=v->call(f,v); apply(vecFunc(anglediff), [[20,45], [-45,45], [-85,90], [-95,90], [-45,125], [-45,145], [29.4803,-88.6381], [-78.3251,-159.036], [-70099.74233810938,29840.67437876723], [-165313.6666297357,33693.9894517456], [1174.8380510598456,-154146.66490124757], [60175.77306795546,42213.07192354373]])</lang>
- Output:
%1 = [25, 90, 175, -175, 170, -170, -118.11840000000000000000000000000000000, -80.710900000000000000000000000000000000, -139.58328312339000000000000000000000023, -72.343918518700000000000000000000000733, -161.50295230741560000000000000000000000, 37.298855588269999999999999999999999909]
Pascal
This program is meant to be saved in the same folder as a file angles.txt containing the input. Each pair of angles to subtract appears on its own line in the input file.
<lang Pascal> Program Bearings; { Reads pairs of angles from a file and subtracts them }
Const
fileName = 'angles.txt';
Type
degrees = real;
Var
subtrahend, minuend: degrees; angleFile: text;
function Simplify(angle: degrees): degrees; { Returns an number in the range [-180.0, 180.0] }
begin
while angle > 180.0 do
angle := angle - 360.0;
while angle < -180.0 do
angle := angle + 360.0;
Simplify := angle
end;
function Difference(b1, b2: degrees): degrees; { Subtracts b1 from b2 and returns a simplified result }
begin Difference := Simplify(b2 - b1) end;
procedure Subtract(b1, b2: degrees); { Subtracts b1 from b2 and shows the whole equation onscreen }
var b3: degrees; begin b3 := Difference(b1, b2); writeln(b2:20:11, ' - ', b1:20:11, ' = ', b3:20:11) end;
Begin
assign(angleFile, fileName);
reset(angleFile);
while not eof(angleFile) do
begin
readln(angleFile, subtrahend, minuend);
Subtract(subtrahend, minuend)
end;
close(angleFile)
End. </lang>
- Input:
20 45
-45 45
-85 90
-95 90
-45 125
-45 145
29.4803 -88.6381
-78.3251 -159.036
-70099.74233810938 29840.67437876723
-165313.6666297357 33693.9894517456
1174.8380510598456 -154146.66490124757
60175.77306795546 42213.07192354373
- Output:
45.00000000000 - 20.00000000000 = 25.00000000000
45.00000000000 - -45.00000000000 = 90.00000000000
90.00000000000 - -85.00000000000 = 175.00000000000
90.00000000000 - -95.00000000000 = -175.00000000000
125.00000000000 - -45.00000000000 = 170.00000000000
145.00000000000 - -45.00000000000 = -170.00000000000
-88.63810000000 - 29.48030000000 = -118.11840000000
-159.03600000000 - -78.32510000000 = -80.71090000000
29840.67437876723 - -70099.74233810938 = -139.58328312339
33693.98945174560 - -165313.66662973570 = -72.34391851869
-154146.66490124760 - 1174.83805105985 = -161.50295230740
42213.07192354373 - 60175.77306795546 = 37.29885558827
Perl
Perl's built-in modulo is integer-only, so import a suitable one from the POSIX core module
<lang perl>use POSIX 'fmod';
sub angle { my($b1,$b2) = @_;
my $b = fmod( ($b2 - $b1 + 720) , 360); $b -= 360 if $b > 180; $b += 360 if $b < -180; return $b;
}
@bearings = (
20, 45, -45, 45, -85, 90, -95, 90, -45, 125, -45, 145, 29.4803, -88.6381, -78.3251, -159.036, -70099.74233810938, 29840.67437876723, -165313.6666297357, 33693.9894517456, 1174.8380510598456, -154146.66490124757, 60175.77306795546, 42213.07192354373
);
while(my ($b1,$b2) = splice(@bearings,0,2)) {
printf "%10.2f %10.2f = %8.2f\n", $b1, $b2, angle($b1,$b2);
} </lang>
- Output:
20.00 45.00 = 25.00
-45.00 45.00 = 90.00
-85.00 90.00 = 175.00
-95.00 90.00 = -175.00
-45.00 125.00 = 170.00
-45.00 145.00 = -170.00
29.48 -88.64 = -118.12
-78.33 -159.04 = -80.71
-70099.74 29840.67 = -139.58
-165313.67 33693.99 = -72.34
1174.84 -154146.66 = -161.50
60175.77 42213.07 = 37.30
Phix
function tz(atom a) -- trim trailing zeroes and decimal point string res = sprintf("%16f",a) for i=length(res) to 1 by -1 do integer ch = res[i] if ch='0' or ch='.' then res[i] = ' ' end if if ch!='0' then exit end if end for return res end function procedure test(atom b1, b2) atom diff = mod(b2-b1,360) diff -= iff(diff>180?360:0) printf(1,"%s %s %s\n",{tz(b1),tz(b2),tz(diff)}) end procedure puts(1," b1 b2 diff\n") puts(1,"---------------- ---------------- ----------------\n") test(20,45) test(-45,45) test(-85,90) test(-95,90) test(-45,125) test(-45,145) test(29.4803,-88.6381) test(-78.3251,-159.036) test(-70099.74233810938,29840.67437876723) test(-165313.6666297357,33693.9894517456) test(1174.8380510598456,-154146.66490124757) test(60175.77306795546,42213.07192354373)
- Output:
b1 b2 diff
---------------- ---------------- ----------------
20 45 25
-45 45 90
-85 90 175
-95 90 -175
-45 125 170
-45 145 -170
29.4803 -88.6381 -118.1184
-78.3251 -159.036 -80.7109
-70099.742338 29840.674379 -139.583283
-165313.66663 33693.989452 -72.343919
1174.838051 -154146.664901 -161.502952
60175.773068 42213.071924 37.298856
Phixmonti
<lang Phixmonti>include ..\Utilitys.pmt
( "16" 1 "16" 1 "16" ) var al
def difAngle /# b1 b2 -- diff #/
swap - 360 mod dup 180 > if 360 - endif
enddef
def test /# b1 b2 -- #/
over over difAngle >ps swap " " rot " " ps> 5 tolist al lalign ?
enddef
( "b1" " " "b2" " " "diff" ) al lalign ? "---------------- ---------------- ----------------" ? 20 45 test -45 45 test -85 90 test -95 90 test -45 125 test -45 145 test 29.4803 -88.6381 test -78.3251 -159.036 test -70099.74233810938 29840.67437876723 test -165313.6666297357 33693.9894517456 test 1174.8380510598456 -154146.66490124757 test 60175.77306795546 42213.07192354373 test</lang>
- Output:
b1 b2 diff
---------------- ---------------- ----------------
20 45 25
-45 45 90
-85 90 175
-95 90 -175
-45 125 170
-45 145 -170
29.4803 -88.638099999999 -118.11840000000
-78.325100000000 -159.03600000000 -80.710899999999
-70099.742338109 29840.6743787672 -139.58328312338
-165313.66662973 33693.9894517455 -72.343918518687
1174.83805105984 -154146.66490124 -161.50295230740
60175.7730679554 42213.0719235437 37.2988555882693
=== Press any key to exit ===
PowerShell
This implementation takes two user inputs with Get-AngleDiff or prints the examples with Get-Examples. There is also a full help file accessed by typing Get-Help Get-AngleDiff -full <lang PowerShell> <# .Synopsis
Gets the difference between two angles between the values of -180 and 180. To see examples use "Get-Examples"
.DESCRIPTION
This code uses the modulo operator, this is represented with the "%". The modulo operator returns the remainder after division, as displayed below 3 % 2 = 1 20 % 15 = 5 200 % 146 = 54
.EXAMPLE
PS C:\WINDOWS\system32> Get-AngleDiff cmdlet Get-AngleDiff at command pipeline position 1 Supply values for the following parameters: angle1: 45 angle2: -85
The difference between 45 and -85 is -130
PS C:\WINDOWS\system32>
.EXAMPLE
PS C:\WINDOWS\system32> Get-AngleDiff -angle1 50 -angle2 -65
The difference between 50 and -65 is -115
PS C:\WINDOWS\system32>
.EXAMPLE
PS C:\WINDOWS\system32> Get-AngleDiff -89 50
The difference between -89 and 50 is 139
PS C:\WINDOWS\system32>
- >
function Get-AngleDiff {
[CmdletBinding()]
Param
(
# Angle one input, must be a number
[Parameter(Mandatory=$true,
ValueFromPipelineByPropertyName=$true)][double]$angle1,
# Angle two input, must be a number
[Parameter(Mandatory=$true,
ValueFromPipelineByPropertyName=$true)][double]$angle2
)
Begin
{
#This is the equation to calculate the difference
[double]$Difference = ($angle2 - $angle1) % 360.0
}
Process
{
#If/IfElse/Else block to return results within the requested range
if ($Difference -lt -180.0)
{$Difference += 360.0
}
elseif ($Difference -gt 360.0)
{$Difference -= 360.0
}
#Writes the values given by the user and the result Write-Host "The difference between $angle1 and $angle2 is $Difference" }
End
{
}
}
<# .Synopsis
This is simply the outputs of the Get-AngleDiff Function in a function
.EXAMPLE PS C:\WINDOWS\system32> Get-Examples
Inputs from the -180 to 180 range The difference between 20 and 45 is 25 The difference between -45 and 45 is 90 The difference between -85 and 90 is 175 The difference between -95 and 90 is 185 The difference between -45 and 125 is 170 The difference between -45 and 145 is 190 The difference between -45 and 125 is 170 The difference between -45 and 145 is 190 The difference between 29.4803 and -88.6381 is -118.1184 The difference between -78.3251 and -159.036 is -80.7109
Inputs from a wider range The difference between -70099.7423381094 and 29840.6743787672 is 220.416716876614 The difference between -165313.666629736 and 33693.9894517456 is 287.656081481313 The difference between 1174.83805105985 and -154146.664901248 is -161.502952307404 The difference between 60175.7730679555 and 42213.0719235437 is 37.2988555882694
PS C:\WINDOWS\system32>
- >
function Get-Examples {
#blank write-host is used for a blank line to make the output look a lil cleaner Write-Host Write-Host "Inputs from the -180 to 180 range"
Get-AngleDiff 20.0 45.0 Get-AngleDiff -45.0 45.0 Get-AngleDiff -85.0 90.0 Get-AngleDiff -95.0 90.0 Get-AngleDiff -45.0 125.0 Get-AngleDiff -45.0 145.0 Get-AngleDiff -45.0 125.0 Get-AngleDiff -45.0 145.0 Get-AngleDiff 29.4803 -88.6381 Get-AngleDiff -78.3251 -159.036 Write-Host Write-Host "Inputs from a wider range"
Get-AngleDiff -70099.74233810938 29840.67437876723 Get-AngleDiff -165313.6666297357 33693.9894517456 Get-AngleDiff 1174.8380510598456 -154146.66490124757 Get-AngleDiff 60175.77306795546 42213.07192354373
}</lang>
Results of user inputs
using -45 and 98 with Get-AngleDiff:
<lang PowerShell>PS C:\WINDOWS\system32> Get-AngleDiff -45 98
The difference between -45 and 98 is 143</lang>
Results of Get-Examples
PS C:\WINDOWS\system32> Get-Examples Inputs from the -180 to 180 range The difference between 20 and 45 is 25 The difference between -45 and 45 is 90 The difference between -85 and 90 is 175 The difference between -95 and 90 is 185 The difference between -45 and 125 is 170 The difference between -45 and 145 is 190 The difference between -45 and 125 is 170 The difference between -45 and 145 is 190 The difference between 29.4803 and -88.6381 is -118.1184 The difference between -78.3251 and -159.036 is -80.7109 Inputs from a wider range The difference between -70099.7423381094 and 29840.6743787672 is 220.416716876614 The difference between -165313.666629736 and 33693.9894517456 is 287.656081481313 The difference between 1174.83805105985 and -154146.664901248 is -161.502952307404 The difference between 60175.7730679555 and 42213.0719235437 is 37.2988555882694
Python
<lang python>from __future__ import print_function
def getDifference(b1, b2): r = (b2 - b1) % 360.0 # Python modulus has same sign as divisor, which is positive here, # so no need to consider negative case if r >= 180.0: r -= 360.0 return r
if __name__ == "__main__": print ("Input in -180 to +180 range") print (getDifference(20.0, 45.0)) print (getDifference(-45.0, 45.0)) print (getDifference(-85.0, 90.0)) print (getDifference(-95.0, 90.0)) print (getDifference(-45.0, 125.0)) print (getDifference(-45.0, 145.0)) print (getDifference(-45.0, 125.0)) print (getDifference(-45.0, 145.0)) print (getDifference(29.4803, -88.6381)) print (getDifference(-78.3251, -159.036))
print ("Input in wider range") print (getDifference(-70099.74233810938, 29840.67437876723)) print (getDifference(-165313.6666297357, 33693.9894517456)) print (getDifference(1174.8380510598456, -154146.66490124757)) print (getDifference(60175.77306795546, 42213.07192354373))</lang>
- Output:
Input in -180 to +180 range 25.0 90.0 175.0 -175.0 170.0 -170.0 170.0 -170.0 -118.11840000000001 -80.71089999999998 Input in wider range -139.58328312338563 -72.34391851868713 -161.50295230740448 37.29885558826936
Or, generalising a little by deriving the degrees from a (Radians -> Radians) function, and formatting the output in columns:
<lang python>Difference between two bearings
from math import (acos, cos, pi, sin)
- bearingDelta :: Radians -> Radians -> Radians
def bearingDelta(ar):
Difference between two bearings,
expressed in radians.
def go(br):
[(ax, ay), (bx, by)] = [
(sin(x), cos(x)) for x in [ar, br]
]
# cross-product > 0 ?
sign = +1 if 0 < ((ay * bx) - (by * ax)) else -1
# sign * dot-product
return sign * acos((ax * bx) + (ay * by))
return lambda br: go(br)
- TEST ----------------------------------------------------
- main :: IO ()
def main():
Test and display
# showMap :: Degrees -> Degrees -> String
def showMap(da, db):
return unwords(
str(x).rjust(n) for n, x in
[
(22, str(da) + ' +'),
(24, str(db) + ' -> '),
(7, round(
degrees(
bearingDelta
(radians(da))
(radians(db))
), 2)
)
]
)
print(__doc__ + ':')
print(
unlines(showMap(a, b) for a, b in [
(20, 45),
(-45, 45),
(-85, 90),
(-95, 90),
(-45, 125),
(-45, 145),
(-70099.74233810938, 29840.67437876723),
(-165313.6666297357, 33693.9894517456),
(1174.8380510598456, -154146.66490124757),
(60175.77306795546, 42213.07192354373)
]))
- GENERIC ----------------------------------------------
- radians :: Float x => Degrees x -> Radians x
def radians(x):
Radians derived from degrees. return pi * x / 180
- degrees :: Float x => Radians x -> Degrees x
def degrees(x):
Degrees derived from radians. return 180 * x / pi
- unlines :: [String] -> String
def unlines(xs):
A single newline-delimited string derived
from a list of strings.
return '\n'.join(xs)
- unwords :: [String] -> String
def unwords(xs):
A space-separated string derived from
a list of words.
return ' '.join(xs)
if __name__ == '__main__':
main()</lang>
- Output:
Difference between two bearings:
20 + 45 -> 25.0
-45 + 45 -> 90.0
-85 + 90 -> 175.0
-95 + 90 -> -175.0
-45 + 125 -> 170.0
-45 + 145 -> -170.0
-70099.74233810938 + 29840.67437876723 -> -139.58
-165313.6666297357 + 33693.9894517456 -> -72.34
1174.8380510598456 + -154146.66490124757 -> -161.5
60175.77306795546 + 42213.07192354373 -> 37.3
Hopefully a lot simpler, elegant and efficient by avoiding conditional statement and trigonometric functions
The table output use print formatting only available from python 3. Tested with 3.6.
<lang python>""" Difference between two bearings """
def delta_bearing(b1 , b2): return ((b2-b1+540)%360)-180
dataSet = [[20, 45], [-45, 45], [-85, 90], [-95, 90], [-45, 125], [-45, 145], \ [29.4803, -88.6381], [-78.3251, -159.036], \ [-70099.74233810938, 29840.67437876723], \ [-165313.6666297357, 33693.9894517456], \ [1174.8380510598456, -154146.66490124757], \ [60175.77306795546, 42213.07192354373]]
print('.{:-^19}.{:-^19}.{:-^9}.' .format(" b1 ", " b2 ", " Δ b " )) for Δ in dataSet: print('|{: > 19}|{: > 19}|{: > 9.4f}|' .format(Δ[0], Δ[1],delta_bearing(Δ[0],Δ[1])))</lang>
- Output:
.------- b1 --------.------- b2 --------.-- Δ b --. | 20| 45| 25.0000| | -45| 45| 90.0000| | -85| 90| 175.0000| | -95| 90|-175.0000| | -45| 125| 170.0000| | -45| 145|-170.0000| | 29.4803| -88.6381|-118.1184| | -78.3251| -159.036| -80.7109| | -70099.74233810938| 29840.67437876723|-139.5833| | -165313.6666297357| 33693.9894517456| -72.3439| | 1174.8380510598456|-154146.66490124757|-161.5030| | 60175.77306795546| 42213.07192354373| 37.2989|
Quackery
Using the Quackery big number rational arithmetic library bigrat.qky.
<lang Quackery> [ $ "bigrat.qky" loadfile ] now!
[ v- -v
proper rot
360 mod
unrot improper
180 1 2over v< iff
[ 360 1 v- ] done
2dup -180 1 v< if
[ 360 1 v+ ] ] is angledelta ( n/d n/d --> n/d )
' [ [ $ "20" $ "45" ]
[ $ "-45" $ "45" ]
[ $ "85" $ "90" ]
[ $ "-95" $ "90" ]
[ $ "-45" $ "125" ]
[ $ "45" $ "145" ]
[ $ "29.4803" $ "-88.6361" ]
[ $ "-78.3251" $ "-159.0360" ]
[ $ "-70099.74233810938" $ "29840.67437876723" ]
[ $ "-165313.6666297357" $ "33693.9894517456" ]
[ $ "1174.8380510598456" $ "-154146.66490124757" ]
[ $ "60175.773067955546" $ "42213.07192354373" ] ]
witheach
[ do
dip [ $->v drop ]
$->v drop
angledelta
20 point$ echo$ cr ]</lang>
- Output:
25 90 5 -175 170 100 -118.1164 -80.7109 -139.58328312339 -72.3439185187 -161.5029523074156 37.298855588184
Racket
see my comments in discussion regards bearing-heading or vice versa
<lang racket>#lang racket (define (% a b) (- a (* b (truncate (/ a b)))))
(define (bearing- bearing heading)
(- (% (+ (% (- bearing heading) 360) 540) 360) 180))
(module+ main
(bearing- 20 45) (bearing- -45 45) (bearing- -85 90) (bearing- -95 90) (bearing- -45 125) (bearing- -45 145) (bearing- 29.4803 -88.6381) (bearing- -78.3251 -159.036)
(bearing- -70099.74233810938 29840.67437876723) (bearing- -165313.6666297357 33693.9894517456) (bearing- 1174.8380510598456 -154146.66490124757) (bearing- 60175.77306795546 42213.07192354373))
(module+ test
(require rackunit)
(check-equal? (% 7.5 10) 7.5) (check-equal? (% 17.5 10) 7.5) (check-equal? (% -7.5 10) -7.5) (check-equal? (% -17.5 10) -7.5))</lang>
- Output:
-25 -90 -175 175 -170 170 118.11839999999995 80.71090000000004 139.58328312338563 72.34391851868713 161.50295230740448 -37.29885558826936
Raku
(formerly Perl 6)
<lang perl6>sub infix:<∠> (Real $b1, Real $b2) {
(my $b = ($b2 - $b1 + 720) % 360) > 180 ?? $b - 360 !! $b;
}
for 20, 45,
-45, 45, -85, 90, -95, 90, -45, 125, -45, 145, 29.4803, -88.6381, -78.3251, -159.036, -70099.74233810938, 29840.67437876723, -165313.6666297357, 33693.9894517456, 1174.8380510598456, -154146.66490124757, 60175.77306795546, 42213.07192354373
-> $b1, $b2 { printf "%10.2f %10.2f = %8.2f\n", $b1, $b2, $b1 ∠ $b2 }</lang>
- Output:
20.00 45.00 = 25.00
-45.00 45.00 = 90.00
-85.00 90.00 = 175.00
-95.00 90.00 = -175.00
-45.00 125.00 = 170.00
-45.00 145.00 = -170.00
29.48 -88.64 = -118.12
-78.33 -159.04 = -80.71
-70099.74 29840.67 = -139.58
-165313.67 33693.99 = -72.34
1174.84 -154146.66 = -161.50
60175.77 42213.07 = 37.30
REXX
Some extra coding was added for a better visual presentation; the angles were centered, the answers were aligned. <lang rexx>/*REXX pgm calculates difference between two angles (in degrees), normalizes the result.*/ numeric digits 25 /*use enough dec. digits for angles*/ call show 20, 45 /*display angular difference (deg).*/ call show -45, 45 /* " " " " */ call show -85, 90 /* " " " " */ call show -95, 90 /* " " " " */ call show -45, 125 /* " " " " */ call show 45, 145 /* " " " " */ call show 29.4803, -88.6361 /* " " " " */ call show -78.3251, -159.036 /* " " " " */ call show -70099.74233810938, 29840.67437876723 /* " " " " */ call show -165313.6666297357, 33693.9894517456 /* " " " " */ call show 1174.8380510598456, -154146.66490124757 /* " " " " */ call show 60175.773067955546, 42213.07192354373 /* " " " " */ exit /*stick a fork in it, we're done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ show: parse arg a,b; d=digits(); $='º' /*obtain the 2 angles (are in degrees).*/
x=format( ( ( ((b-a) // 360) + 540) // 360) - 180, 4, d) /*compute and format. */
if pos(., x)\==0 then x=strip( strip(x, 'T', 0), "T", .) /*strip trailing chaff.*/
say center(a || $, d) '─' center(b || $, d) " ────► " x || $
return /* [↑] display the angular difference.*/</lang>
- output:
20º ─ 45º ────► 25º
-45º ─ 45º ────► 90º
-85º ─ 90º ────► 175º
-95º ─ 90º ────► -175º
-45º ─ 125º ────► 170º
45º ─ 145º ────► 100º
29.4803º ─ -88.6361º ────► -118.1164º
-78.3251º ─ -159.036º ────► -80.7109º
-70099.74233810938º ─ 29840.67437876723º ────► -139.58328312339º
-165313.6666297357º ─ 33693.9894517456º ────► -72.3439185187º
1174.8380510598456º ─ -154146.66490124757º ────► -161.5029523074156º
60175.773067955546º ─ 42213.07192354373º ────► 37.298855588184º
Ring
<lang ring>
- Project : Angle difference between two bearings
decimals(4) see "Input in -180 to +180 range:" + nl see getDifference(20.0, 45.0) + nl see getDifference(-45.0, 45.0) + nl see getDifference(-85.0, 90.0) + nl see getDifference(-95.0, 90.0) + nl see getDifference(-45.0, 125.0) + nl see getDifference(-45.0, 145.0) + nl see getDifference(-45.0, 125.0) + nl see getDifference(-45.0, 145.0) + nl see getDifference(29.4803, -88.6381) + nl see getDifference(-78.3251, -159.036) + nl
func getDifference(b1, b2)
r = (b2 - b1) % 360.0
if r >= 180.0
r = r - 360.0
end
return r
</lang> Output:
Input in -180 to +180 range: 25 90 175 -175 170 -170 170 -170 -118.1184 -80.7109
Ruby
<lang ruby>def getDifference(b1, b2) r = (b2 - b1) % 360.0 # Ruby modulus has same sign as divisor, which is positive here, # so no need to consider negative case if r >= 180.0 r -= 360.0 end return r end
if __FILE__ == $PROGRAM_NAME puts "Input in -180 to +180 range" puts getDifference(20.0, 45.0) puts getDifference(-45.0, 45.0) puts getDifference(-85.0, 90.0) puts getDifference(-95.0, 90.0) puts getDifference(-45.0, 125.0) puts getDifference(-45.0, 145.0) puts getDifference(-45.0, 125.0) puts getDifference(-45.0, 145.0) puts getDifference(29.4803, -88.6381) puts getDifference(-78.3251, -159.036)
puts "Input in wider range" puts getDifference(-70099.74233810938, 29840.67437876723) puts getDifference(-165313.6666297357, 33693.9894517456) puts getDifference(1174.8380510598456, -154146.66490124757) puts getDifference(60175.77306795546, 42213.07192354373) end</lang>
- Output:
Input in -180 to +180 range 25.0 90.0 175.0 -175.0 170.0 -170.0 170.0 -170.0 -118.11840000000001 -80.71089999999998 Input in wider range -139.58328312338563 -72.34391851868713 -161.50295230740448 37.29885558826936
Rust
<lang rust> /// Calculate difference between two bearings, in -180 to 180 degrees range pub fn angle_difference(bearing1: f64, bearing2: f64) -> f64 {
let diff = (bearing2 - bearing1) % 360.0;
if diff < -180.0 {
360.0 + diff
} else if diff > 180.0 {
-360.0 + diff
} else {
diff
}
}
- [cfg(test)]
mod tests {
use super::*;
#[test]
fn test_angle_difference() {
assert_eq!(25.00, angle_difference(20.00, 45.00));
assert_eq!(90.00, angle_difference(-45.00, 45.00));
assert_eq!(175.00, angle_difference(-85.00, 90.00));
assert_eq!(-175.00, angle_difference(-95.00, 90.00));
assert_eq!(170.00, angle_difference(-45.00, 125.00));
assert_eq!(-170.00, angle_difference(-45.00, 145.00));
approx_eq(-118.1184, angle_difference(29.4803, -88.6381));
approx_eq(-80.7109, angle_difference(-78.3251 , -159.036));
approx_eq(-139.5832, angle_difference(-70099.74233810938, 29840.67437876723));
approx_eq(-72.3439, angle_difference(-165313.6666297357, 33693.9894517456));
approx_eq(-161.5029, angle_difference(1174.8380510598456, -154146.66490124757));
approx_eq(37.2988, angle_difference(60175.77306795546, 42213.07192354373));
}
// approximate equality on floats. // see also https://crates.io/crates/float-cmp fn approx_eq(f1: f64, f2: f64) { assert!((f2-f1).abs() < 0.0001, "{} != {}", f1, f2) }
} </lang>
Scala
- Output:
Best seen running in your browser either by ScalaFiddle (ES aka JavaScript, non JVM) or Scastie (remote JVM).
<lang Scala>object AngleDifference extends App {
private def getDifference(b1: Double, b2: Double) = {
val r = (b2 - b1) % 360.0
if (r < -180.0) r + 360.0 else if (r >= 180.0) r - 360.0 else r
}
println("Input in -180 to +180 range")
println(getDifference(20.0, 45.0))
println(getDifference(-45.0, 45.0))
println(getDifference(-85.0, 90.0))
println(getDifference(-95.0, 90.0))
println(getDifference(-45.0, 125.0))
println(getDifference(-45.0, 145.0))
println(getDifference(-45.0, 125.0))
println(getDifference(-45.0, 145.0))
println(getDifference(29.4803, -88.6381))
println(getDifference(-78.3251, -159.036))
println("Input in wider range")
println(getDifference(-70099.74233810938, 29840.67437876723))
println(getDifference(-165313.6666297357, 33693.9894517456))
println(getDifference(1174.8380510598456, -154146.66490124757))
println(getDifference(60175.77306795546, 42213.07192354373))
}</lang>
Scheme
R6RS standard. <lang scheme>#!r6rs
(import (rnrs base (6))
(rnrs io simple (6)))
(define (bearing-difference bearing-2 bearing-1)
(- (mod (+ (mod (- bearing-2 bearing-1)
360)
540)
360)
180))
(define (bearing-difference-test)
(define test-cases
'((20 45)
(-45 45)
(-85 90)
(-95 90)
(-45 125)
(-45 145)
(29.4803 -88.6381)
(-78.3251 -159.036)
(-70099.74233810938 29840.67437876723)
(-165313.6666297357 33693.9894517456)
(1174.8380510598456 -154146.66490124757)
(60175.77306795546 42213.07192354373)))
(for-each
(lambda (argument-list)
(display (apply bearing-difference argument-list))
(newline))
test-cases))</lang>
- Output:
> (bearing-difference-test) -25 -90 -175 175 -170 170 118.11839999999995 80.71090000000004 139.58328312338563 72.34391851868713 161.50295230740448 -37.29885558826936
Seed7
The library float.s7i supports the operator mod, which can be used to solve this task easily.
<lang seed7>$ include "seed7_05.s7i";
include "float.s7i";
const func float: getDifference (in float: b1, in float: b2) is func
result
var float: difference is 0.0;
begin
difference := (b2 - b1) mod 360.0;
if difference > 180.0 then
difference -:= 360.0;
end if;
end func;
const proc: main is func
begin
writeln("Input in -180 to +180 range");
writeln(getDifference(20.0, 45.0));
writeln(getDifference(-45.0, 45.0));
writeln(getDifference(-85.0, 90.0));
writeln(getDifference(-95.0, 90.0));
writeln(getDifference(-45.0, 125.0));
writeln(getDifference(-45.0, 145.0));
writeln(getDifference(-45.0, 125.0));
writeln(getDifference(-45.0, 145.0));
writeln(getDifference(29.4803, -88.6381));
writeln(getDifference(-78.3251, -159.036));
writeln("Input in wider range");
writeln(getDifference(-70099.74233810938, 29840.67437876723));
writeln(getDifference(-165313.6666297357, 33693.9894517456));
writeln(getDifference(1174.8380510598456, -154146.66490124757));
writeln(getDifference(60175.77306795546, 42213.07192354373));
end func;</lang>
- Output:
Input in -180 to +180 range 25.0 90.0 175.0 -175.0 170.0 -170.0 170.0 -170.0 -118.1184 -80.7109 Input in wider range -139.583283123386 -72.3439185186871 -161.502952307404 37.2988555882694
Sidef
<lang ruby>func bearingAngleDiff(b1, b2) {
(var b = ((b2 - b1 + 720) % 360)) > 180 ? (b - 360) : b
}
printf("%25s %25s %25s\n", "B1", "B2", "Difference") printf("%25s %25s %25s\n", "-"*20, "-"*20, "-"*20)
for b1,b2 in ([
20, 45
-45, 45
-85, 90
-95, 90
-45, 125
-45, 145
29.4803, -88.6381
-78.3251, -159.036
-70099.74233810938, 29840.67437876723
-165313.6666297357, 33693.9894517456
1174.8380510598456, -154146.66490124757
60175.77306795546, 42213.07192354373
].slices(2)
) {
printf("%25s %25s %25s\n", b1, b2, bearingAngleDiff(b1, b2))
}</lang>
- Output:
B1 B2 Difference
-------------------- -------------------- --------------------
20 45 25
-45 45 90
-85 90 175
-95 90 -175
-45 125 170
-45 145 -170
29.4803 -88.6381 -118.1184
-78.3251 -159.036 -80.7109
-70099.74233810938 29840.67437876723 -139.58328312339
-165313.6666297357 33693.9894517456 -72.3439185187
1174.8380510598456 -154146.66490124757 -161.5029523074156
60175.77306795546 42213.07192354373 37.29885558827
Swift
<lang swift>func angleDifference(a1: Double, a2: Double) -> Double {
let diff = (a2 - a1).truncatingRemainder(dividingBy: 360)
if diff < -180.0 {
return 360.0 + diff
} else if diff > 180.0 {
return -360.0 + diff
} else {
return diff
}
}
let testCases = [
(20.0, 45.0), (-45, 45), (-85, 90), (-95, 90), (-45, 125), (-45, 145), (29.4803, -88.6381), (-78.3251, -159.036), (-70099.74233810938, 29840.67437876723), (-165313.6666297357, 33693.9894517456), (1174.8380510598456, -154146.66490124757), (60175.77306795546, 42213.07192354373)
]
print(testCases.map(angleDifference))</lang>
- Output:
[25.0, 90.0, 175.0, -175.0, 170.0, -170.0, -118.1184, -80.7109, -139.58328312338563, -72.34391851868713, -161.50295230740448, 37.29885558826936]
Tcl
<lang tcl> proc angleDiff {b1 b2} {
set angle [::tcl::mathfunc::fmod [expr ($b2 - $b1)] 360]
if {$angle < -180.0} {
set angle [expr $angle + 360.0]
}
if {$angle >= 180.0} {
set angle [expr $angle - 360.0]
}
return $angle
}
puts "Input in -180 to +180 range" puts [angleDiff 20.0 45.0] puts [angleDiff -45.0 45.0] puts [angleDiff -85.0 90.0] puts [angleDiff -95.0 90.0] puts [angleDiff -45.0 125.0] puts [angleDiff -45.0 145.0] puts [angleDiff -45.0 125.0] puts [angleDiff -45.0 145.0] puts [angleDiff 29.4803 -88.6381] puts [angleDiff -78.3251 -159.036]
puts "Input in wider range" puts [angleDiff -70099.74233810938 29840.67437876723] puts [angleDiff -165313.6666297357 33693.9894517456] puts [angleDiff 1174.8380510598456 -154146.66490124757] puts [angleDiff 60175.77306795546 42213.07192354373] </lang>
- Output:
Input in -180 to +180 range 25.0 90.0 175.0 -175.0 170.0 -170.0 170.0 -170.0 -118.1184 -80.7109 Input in wider range -139.58328312338563 -72.34391851868713 -161.50295230740448 37.29885558826936
VBA
<lang vb>Private Function tx(a As Variant) As String
Dim s As String
s = CStr(Format(a, "0.######"))
If Right(s, 1) = "," Then
s = Mid(s, 1, Len(s) - 1) & " "
Else
i = InStr(1, s, ",")
s = s & String$(6 - Len(s) + i, " ")
End If
tx = s
End Function Private Sub test(b1 As Variant, b2 As Variant)
Dim diff As Variant diff = (b2 - b1) - ((b2 - b1) \ 360) * 360 diff = diff - IIf(diff > 180, 360, 0) diff = diff + IIf(diff < -180, 360, 0) Debug.Print Format(tx(b1), "@@@@@@@@@@@@@@@@"); Format(tx(b2), "@@@@@@@@@@@@@@@@@"); Format(tx(diff), "@@@@@@@@@@@@@@@@@")
End Sub Public Sub angle_difference()
Debug.Print " b1 b2 diff" Debug.Print "---------------- ---------------- ----------------" test 20, 45 test -45, 45 test -85, 90 test -95, 90 test -45, 125 test -45, 145 test 29.4803, -88.6381 test -78.3251, -159.036 test -70099.7423381094, 29840.6743787672 test -165313.666629736, 33693.9894517456 test 1174.83805105985, -154146.664901248 test 60175.7730679555, 42213.0719235437
End Sub</lang>
- Output:
b1 b2 diff
---------------- ---------------- ----------------
20 45 25
-45 45 90
-85 90 175
-95 90 -175
-45 125 170
-45 145 -170
29,4803 -88,6381 -118,1184
-78,3251 -159,036 -80,7109
-70099,742338 29840,674379 -139,583283
-165313,66663 33693,989452 -72,343919
1174,838051 -154146,664901 -161,502952
60175,773068 42213,071924 37,298856
Visual Basic .NET
<lang vbnet>Module Module1
Function Delta_Bearing(b1 As Decimal, b2 As Decimal) As Decimal
Dim d As Decimal = 0
' Convert bearing to W.C.B
While b1 < 0
b1 += 360
End While
While b1 > 360
b1 -= 360
End While
While b2 < 0
b2 += 360
End While
While b2 > 0
b2 -= 360
End While
' Calculate delta bearing
d = (b2 - b1) Mod 360
' Convert result to Q.B
If d > 180 Then
d -= 360
ElseIf d < -180 Then
d += 360
End If
Return d End Function
Sub Main()
' Calculate standard test cases
Console.WriteLine(Delta_Bearing(20, 45))
Console.WriteLine(Delta_Bearing(-45, 45))
Console.WriteLine(Delta_Bearing(-85, 90))
Console.WriteLine(Delta_Bearing(-95, 90))
Console.WriteLine(Delta_Bearing(-45, 125))
Console.WriteLine(Delta_Bearing(-45, 145))
Console.WriteLine(Delta_Bearing(29.4803, -88.6381))
Console.WriteLine(Delta_Bearing(-78.3251, -159.036))
' Calculate optional test cases
Console.WriteLine(Delta_Bearing(-70099.742338109383, 29840.674378767231))
Console.WriteLine(Delta_Bearing(-165313.6666297357, 33693.9894517456))
Console.WriteLine(Delta_Bearing(1174.8380510598456, -154146.66490124757))
Console.WriteLine(Delta_Bearing(60175.773067955459, 42213.071923543728))
End Sub
End Module</lang>
- Output:
25 90 175 -175 170 -170 -118.1184 -80.7109 -139.5832831234 -72.3439185184 -161.50295230785 37.2988555882
Wren
<lang ecmascript>var subtract = Fn.new { |b1, b2|
var d = (b2 - b1) % 360 if (d < -180) d = d + 360 if (d >= 180) d = d - 360 return (d * 10000).round / 10000 // to 4dp
}
var pairs = [
[ 20, 45], [-45, 45], [-85, 90], [-95, 90], [-45, 125], [-45, 145], [ 29.4803, -88.6381], [-78.3251, -159.036], [-70099.74233810938, 29840.67437876723], [-165313.6666297357, 33693.9894517456], [1174.8380510598456, -154146.66490124757], [60175.77306795546, 42213.07192354373]
]
System.print("Differences (to 4dp) between these bearings:") for (pair in pairs) {
var p0 = pair[0]
var p1 = pair[1]
var diff = subtract.call(p0, p1)
var offset = (p0 < 0) ? " " : " "
System.print("%(offset)%(p0) and %(p1) -> %(diff)")
}</lang>
- Output:
Differences (to 4dp) between these bearings: 20 and 45 -> 25 -45 and 45 -> 90 -85 and 90 -> 175 -95 and 90 -> -175 -45 and 125 -> 170 -45 and 145 -> -170 29.4803 and -88.6381 -> -118.1184 -78.3251 and -159.036 -> -80.7109 -70099.742338109 and 29840.674378767 -> -139.5833 -165313.66662974 and 33693.989451746 -> -72.3439 1174.8380510598 and -154146.66490125 -> -161.503 60175.773067955 and 42213.071923544 -> 37.2989
XPL0
Pairs of bearing angles are input from the console or from a file (terminated with Ctrl+C) redirected on the command line. <lang XPL0>real B1, B2, Ang; [Text(0, " Bearing 1 Bearing 2 Difference"); loop [B1:= RlIn(1);
B2:= RlIn(1);
Ang:= B2 - B1;
while Ang > 180. do Ang:= Ang - 360.;
while Ang < -180. do Ang:= Ang + 360.;
CrLf(0);
RlOut(0, B1); ChOut(0, 9);
RlOut(0, B2); ChOut(0, 9);
RlOut(0, Ang);
];
]</lang>
- Output:
Bearing 1 Bearing 2 Difference 20.00000 45.00000 25.00000 -45.00000 45.00000 90.00000 -85.00000 90.00000 175.00000 -95.00000 90.00000 -175.00000 -45.00000 125.00000 170.00000 -45.00000 145.00000 -170.00000 29.48030 -88.63810 -118.11840 -78.32510 -159.03600 -80.71090 -70099.74234 29840.67438 -139.58328 -165313.66663 33693.98945 -72.34392 1174.83805 -154146.66490 -161.50295 60175.77307 42213.07192 37.29886
zkl
<lang zkl>fcn bearingAngleDiff(b1,b2){ // -->Float, b1,b2 can be int or float
( (b:=(0.0 + b2 - b1 + 720)%360) > 180 ) and b - 360 or b;
}</lang> <lang zkl>T( 20,45, -45,45, -85,90, -95,90, -45,125, -45,145 ) .pump(Console.println,Void.Read,
fcn(b1,b2){ "%.1f\UB0; + %.1f\UB0; = %.1f\UB0;"
.fmt(b1,b2,bearingAngleDiff(b1,b2)) });</lang>
- Output:
20.0° + 45.0° = 25.0° -45.0° + 45.0° = 90.0° -85.0° + 90.0° = 175.0° -95.0° + 90.0° = -175.0° -45.0° + 125.0° = 170.0° -45.0° + 145.0° = -170.0°
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