Increment a numerical string: Difference between revisions

</pre>

=={{header|Free Pascal}}==

not like [[#Delphi|Delphi]] doing two conversion, but increment a string by 1 is much faster.

Here with different bases upto 10.After this there must be a correction to convert values > '9' to 'A'...

Only for positive integer strings as high speed counter.

<lang pascal>program StrInc;

//increments a positive numerical string in different bases.

//the string must be preset with a value, length >0 ;

{$IFDEF WINDOWS}

{$APPTYPE CONSOLE}

{$ENDIF}

{$IFDEF FPC}

{$Mode Delphi} {$Optimization ON,ALL}{$Align 32}

uses

sysutils;

{$ELSE}

uses

system.SysUtils;

{$ENDIF}

type

myString = AnsiString; // string[32];//

function IncLoop(ps: pChar;le,Base: NativeInt):NativeInt;inline;

//Add 1 and correct carry

//returns 0, if no overflow, else -1

var

dg: nativeInt;

Begin

dec(le);//ps is 0-based

repeat

dg := ord(ps[le])+(-ord('0')+1);

result := -ord(dg>=base);// -1 or 0 -> $FF...FF or $00...00

ps[le] := chr(-(result AND base)+dg+ord('0'));

dec(le);

until (result = 0) or (le<0);

end;

procedure IncIntStr(base:NativeInt;var s:myString);

begin

//overflow -> prepend a '1' to string

if (IncLoop(pChar(@s[1]),length(s),base) <>0) then

s := '1'+s;

end;

const

ONE_BILLION = 1000*1000*1000;

strLen = 26;

MAX = 1 shl strLen -1;

var

s : myString;

i,base : nativeInt;

T0: TDateTime;

Begin

writeln(MAX,' increments in base');

For base := 2 to 10 do

Begin

//s := '0' doesn't work

setlength(s,1);

s[1]:= '0';

{ //Zero pad string

setlength(s,strLen);fillchar(s[1],strLen,'0');

}

T0 := time;

For i := 1 to MAX do

IncIntStr(Base,s);

T0 := (time-T0)*86400;

writeln(s:strLen,' base ',base:2,T0:8:3,' s');

end;

writeln;

writeln('One billion digits "9"');

setlength(s,ONE_BILLION+1);

s[1]:= '0';//don't measure setlength in IncIntStr

fillchar(s[2],length(s)-1,'9');

writeln('first 5 digits ',s[1],s[2],s[3],s[4],s[5]);

T0 := time;

IncIntStr(10,s);

T0 := (time-T0)*86400;

writeln(length(s):10,T0:8:3,' s');

writeln('first 5 digits ',s[1],s[2],s[3],s[4],s[5]);

s:='';

{$IFDEF WINDOWS}

readln;

{$ENDIF}

end.

</lang>

{{out|@TIO.RUN}}

<pre>

67108863 increments in base

11111111111111111111111111 base 2 0.451 s

11200021111001110 base 3 0.394 s

3333333333333 base 4 0.339 s

114134440423 base 5 0.363 s

10354213103 base 6 0.358 s

1443262443 base 7 0.320 s

377777777 base 8 0.310 s

150244043 base 9 0.308 s

67108863 base 10 0.301 s // without inline 0.364

One billion digits "9"

first 5 digits 09999

1000000001 1.813 s

first 5 digits 10000