Question

How to replace the first occurrence of a substring in a string with Pascal

Answer 1

program ReplaceFirstOccurrence;

procedure ReplaceFirstOccurrence(var str: string; const oldSub, newSub: string);
var
  posIndex: Integer;
  beforePart, afterPart: string;
begin
  posIndex := Pos(oldSub, str);
  if posIndex > 0 then
  begin
    beforePart := Copy(str, 1, posIndex - 1);
    afterPart := Copy(str, posIndex + Length(oldSub), Length(str));
    str := beforePart + newSub + afterPart;
  end;
end;

var
  str: string;
  oldSub, newSub: string;
begin
  str := 'aa bb cc dd ee cc';
  oldSub := 'cc';
  newSub := 'YY';

  ReplaceFirstOccurrence(str, oldSub, newSub);
  WriteLn(str);
end.



   
(*
run:
  
aa bb YY dd ee cc
  
*)

 

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