[fpc-pascal]feature request: enhanced "pos"

[Jeff Pohlmeyer]

> Dunno if this is the right place to post such a message, but here goes...
 
> I would love to see a "pos" function that takes an additional parameter, being 
> the position in the string where it should START scanning. e.g.:
 
> my_str = 'Hello, everybody... Hello, world!';
> x := pos ('Hello', my_str, 6);
 
> So it starts scanning at position 6 (after the first Hello) and finds the 
> second Hello at position 21; returns 21.   (not 21-6)
 
> Passing it a starting position 2 (instead of 6) would also skip the first 
> Hello, and return the same 21.
 
> (( Of course, passing it a starting position greater than the length(str) - 
> length(target) should return 0; also it should return 0 if the target is not found 
> between startpos and the end of the string. ))


Dunno if this is the right place to post such an answer, but here goes...


program postest;
{$H+}{$MODE OBJFPC}
uses strings;

function PosFrom( const needle:AnsiString; const haystack:AnsiString; 
                  StartPt:LongInt):LongInt;
var
  p:pChar;
begin
  Result:=0;
  if (StartPt <= Length(haystack)) 
  then begin 
    p:=StrPos(pChar(@haystack[StartPt]), pChar(needle));
    if ( p <> nil ) then Result:= ( p - @haystack[1] ) + 1;
  end
end;


// Testing ...

var
  subject, pattern : string;
  i:integer;
begin
  subject := 'Hello, everybody... Hello, world!';
  pattern := 'Hello';
  for i:=1 to length(subject) do
     WriteLn('Position from ', i, ' is ',  PosFrom(pattern, subject, i));
end.


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