Temperature conversion

Temperature conversion is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

There are quite a number of temperature scales. For this task we will concentrate on 4 of the perhaps best-known ones: Kelvin, Celcius, Fahrenheit and Rankine.

The Celcius and Kelvin scales have the same magnitude, but different null points.

0 degrees Celcius corresponds to 273.15 kelvin.

0 kelvin is absolute zero.

The Fahrenheit and Rankine scales also have the same magnitude, but different null points.

0 degrees Fahrenheit corresponds to 459.67 degrees Rankine.

0 degrees Rankine is absolute zero.

The Celcius/Kelvin and Fahrenheit/Rankine scales have a ratio of 5 : 9.

Write code that accepts a value of kelvin, converts it to values on the three other scales and prints the result. For instance:

K  21.00

C  -252.15

F  -421.87

R  37.80

D

<lang d>double kelvinToCelsius(in double k) pure nothrow @safe {

   return k - 273.15;

}

double kelvinToFahrenheit(in double k) pure nothrow @safe {

   return k * 1.8 - 459.67;

}

double kelvinToRankine(in double k) pure nothrow @safe {

   return k * 1.8;

}

unittest {

   import std.math: approxEqual;
   assert(approxEqual(kelvinToCelsius(21.0), -252.15));
   assert(approxEqual(kelvinToFahrenheit(21.0), -421.87));
   assert(approxEqual(kelvinToRankine(21.0), 37.8));

}

void main(string[] args) {

   import std.stdio, std.conv, std.string;

   if (args.length == 2 && isNumeric(args[1])) {
       immutable kelvin = to!double(args[1]);
       if (kelvin >= 0) {
           writefln("K  %2.2f", kelvin);
           writefln("C  %2.2f", kelvinToCelsius(kelvin));
           writefln("F  %2.2f", kelvinToFahrenheit(kelvin));
           writefln("R  %2.2f", kelvinToRankine(kelvin));
       } else
           writefln("%2.2f K is below absolute zero", kelvin);
   }

}</lang>

Output:

K  21.00

C  -252.15

F  -421.87

R  37.80

J

Solution:<lang j> NB. Temp conversions are all linear polynomials

  K2K    =:     0    1    NB. K = (1  *k) +   0
  K2C    =:  _273    1    NB. C = (1  *k) - 273
  K2F    =:  _459.67 1.8  NB. F = (1.8*k) - 459.67
  K2R    =:     0    1.8  NB. R = (1.8*k) +   0

  NB.  Do all conversions at once (eval 
  NB.  polynomials in parallel). This is the
  NB.  numeric matrix J programs would manipulate
  NB.  directly.
  k2KCFR =:  (K2K , K2C , K2F ,: K2R) p./ ]</lang>

Example:<lang j> NB. Format matrix for printing

  fmt    =:  '0.2' 8!:0 k2KCFR

  NB.  Tag each temp with scale, for human
  NB.  legibility.
  kcfr   =:  0 _1 |: 'KCFR' ,"0 1"_1 >@:fmt
  
  kcfr 21

K 21.00 C-252.00 F-421.87 R 37.80

  kcfr 0 NB. Absolute zero

K 0.00 C-273.00 F-459.67 R 0.00

  kcfr 21 100 300  NB. List of temps works fine

K 21.00 C-252.00 F-421.87 R 37.80

K 100.00 C-173.00 F-279.67 R 180.00

K 300.00 C 27.00 F 80.33 R 540.00

  </lang>

Notes: The approach is founded on polynomials, one for each conversion (e.g. Fahrenheit = 1.8*x - 459.67 where x is measured in degrees Kelvin), and all polynomials are evaluated simultaneously using the built-in p.. Through some code decorations (specifically the / in p./ the "0 1"_1 and the 0 _1 |:), we permit our function to convert arrays of temperatures of arbitrarily high dimension (a single temp, lists of temps, tables of temps, cubes of temps, etc).

Java

<lang java>public class TemperatureConversion {

   public static void main(String args[]) {
       if (args.length == 1) {
           try {
               double kelvin = Double.parseDouble(args[0]);
               if (kelvin >= 0) {
                   System.out.printf("K  %2.2f\n", kelvin);
                   System.out.printf("C  %2.2f\n", kelvinToCelcius(kelvin));
                   System.out.printf("F  %2.2f\n", kelvinToFahrenheit(kelvin));
                   System.out.printf("R  %2.2f\n", kelvinToRankine(kelvin));
               } else {
                   System.out.printf("%2.2f K is below absolute zero", kelvin);
               }
           } catch (NumberFormatException e) {
               System.out.println(e);
           }
       }
   }

   public static double kelvinToCelcius(double k) {
       return k + 273.15;
   }

   public static double kelvinToFahrenheit(double k) {
       return k * 1.8 - 459.67;
   }

   public static double kelvinToRankine(double k) {
       return k * 1.8;
   }

}</lang>

K  21.00

C  -252.15

F  -421.87

R  37.80

PHP

<lang php>error_reporting(E_ALL & ~ ( E_NOTICE | E_WARNING ));

while (true) {

   echo "\nEnter a value in kelvin (q to quit): ";
   if (($kelvin = trim(fgets(STDIN))) !== false) {
       if ($kelvin == 'q') {
           echo 'quitting';
           break;
       }
       if (is_numeric($kelvin)) {
           $kelvin = floatVal($kelvin);
           if ($kelvin >= 0) {
               printf(" K  %2.2f\n", $kelvin);
               printf(" C  %2.2f\n", $kelvin - 273.15);
               printf(" F  %2.2f\n", $kelvin * 1.8 - 459.67);
               printf(" R  %2.2f\n", $kelvin * 1.8);
           } else printf(" %2.2f K is below absolute zero\n", $kelvin);
       }
   }

}</lang>

Enter a value in kelvin (q to quit): 21
 K  21.00
 C  -252.15
 F  -421.87
 R  37.80

Enter a value in kelvin (q to quit): q
quitting

Python

<lang python>>>> while True: k = float(input('K ? ')) print("%g Kelvin = %g Celsius = %g Fahrenheit = %g Rankine degrees."  % (k, k - 273.15, k * 1.8 - 459.67, k * 1.8))

K ? 21.0 21 Kelvin = -252.15 Celsius = -421.87 Fahrenheit = 37.8 Rankine degrees. K ? 222.2 222.2 Kelvin = -50.95 Celsius = -59.71 Fahrenheit = 399.96 Rankine degrees. K ? </lang>

Python: Universal conversion

This converts from any one of the units to all the others <lang python>>>> toK = {'C': (lambda c: c + 273.15),

          'F': (lambda f: (f + 459.67) / 1.8),
          'R': (lambda r: r / 1.8),
          'K': (lambda k: k) }

>>> while True: magnitude, unit = input('<value> <K/R/F/C> ? ').split() k = toK[unit](float(magnitude)) print("%g Kelvin = %g Celsius = %g Fahrenheit = %g Rankine degrees."  % (k, k - 273.15, k * 1.8 - 459.67, k * 1.8))

<value> <K/R/F/C> ? 222.2 K 222.2 Kelvin = -50.95 Celsius = -59.71 Fahrenheit = 399.96 Rankine degrees. <value> <K/R/F/C> ? -50.95 C 222.2 Kelvin = -50.95 Celsius = -59.71 Fahrenheit = 399.96 Rankine degrees. <value> <K/R/F/C> ? -59.71 F 222.2 Kelvin = -50.95 Celsius = -59.71 Fahrenheit = 399.96 Rankine degrees. <value> <K/R/F/C> ? 399.96 R 222.2 Kelvin = -50.95 Celsius = -59.71 Fahrenheit = 399.96 Rankine degrees. <value> <K/R/F/C> ? </lang>

REXX

This REXX version supports:

• (alternate spellings with optional   degrees):
  • Centingrade, centesimal, Celsius, Celcius
  • Fahrenheit
  • Kelvin
  • Rankine
  • Reaumur
• multiple temperatures in a list
• comments within the list
• aligned output (whole numbers and decimal fractions)

<lang rexx>/*REXX program converts units of temperature for: C, F, R, Re, K. */ parse arg tList /*get specified temperature lists*/

 do  until  tList=                  /*process a list of temperatures.*/
 parse  var tList  x  ','  tList      /*temps are separated by commas. */
 x=space(x);  parse var x z '('       /*handle any comments (if any).  */
 if z==     then call serr 'no arguments were specified.'
 _ = verify(z, '+-.0123456789')       /*all the legal number thingys.  */

 if _\==0  then do
                if _==1  then call serr 'illegal temperature:'  #
                n= left(z,_-1)        /*pick off the number (hopefully)*/
                u= strip(substr(z,_)) /*pick off the temperature unit. */
                end
           else u= 'k'                /*assume  Kelvin as per task req.*/

 uU=u;  upper uU                      /*uppercase version of temp unit.*/
 if left(uU,7)=='DEGREES' then uU=substr(uU,8)  /*reduntant "degrees"? */
 if left(uU,5)=='DEGREE'  then uU=substr(uU,7)  /*reduntant "degree" ? */
 uU=strip(uU)
 if \datatype(n,'N')  then call serr 'illegal number:' n
                                      /*accept alternate spellings.    */
            select                    /*convert ───◄ common temperature*/
            when abbrev('CENTIGRADE', uU) |,
                 abbrev('CENTESIMAL', uU) |,
                 abbrev('CELSIUS'   , uU) |,
                 abbrev('CELCIUS'   , uU)     then F = n * 1.8   +  32
            when abbrev('FAHRENHEIT', uU)     then F = n
            when abbrev('KELVIN'    , uU)     then F = n * 1.8   - 459.67
            when abbrev('RANKINE'   , uU)     then F = n         - 459.67
            when abbrev('REAUMUR'   , uU, 2)  then F = n * 2.25  +  32
            otherwise     call serr  'illegal temperature scale:'  u
            end   /*select*/
                                                  say right(' ' x,55,"─")
 say Tform((F - 32)      / 1.8  )   'Celcius'
 say Tform( F                   )   'Fahrenheit'
 say Tform((F + 459.67)  * 1.8  )   'Kelvin'
 say Tform( F + 459.67          )   'Rankine'
 say Tform((F - 32    )  / 2.25 )   'Reaumur'
 end   /*until tlist=*/

exit /*stick a fork in it, we're done.*/ /*──────────────────────────────────TFORM subroutine────────────────────*/ Tform: procedure; showDig=3; _=format(arg(1),,showDig)/1; p=pos('.',_) if p==0 then _=_ || left(,showDig+1)

        else _=_ || left(,showDig-length(_)+p);      return right(_,20)

/*──────────────────────────────────SERR subroutine─────────────────────*/ serr: say; say '***error!***'; say; say arg(1); say; exit 13</lang> output when using the input of: -40C, 0 c (water freezes), 37C (body temp), 100 C (water boils), 21 degrees Kelvin, 0K (outer space?)