Question

How to remove comments from a string in Pascal

Answer 1

program RemoveComments;

function StripComments(const S: string): string;
var
  i: Integer;
  OutStr: string;
begin
  i := 1;
  OutStr := '';

  while i <= Length(S) do
  begin
    // Check for // comment
    if (i < Length(S)) and (S[i] = '/') and (S[i+1] = '/') then
    begin
      Inc(i, 2);
      while (i <= Length(S)) and (S[i] <> #10) do
        Inc(i);
    end

    // Check for (* ... *) comment
    else if (i < Length(S)) and (S[i] = '(') and (S[i+1] = '*') then
    begin
      Inc(i, 2);
      while (i < Length(S)) and not ((S[i] = '*') and (S[i+1] = ')')) do
        Inc(i);
      if i < Length(S) then Inc(i, 2);
    end

    // Normal character
    else
    begin
      OutStr := OutStr + S[i];
      Inc(i);
    end;
  end;

  StripComments := OutStr;
end;

var
  Input, OutputStr: string;

begin
  Input :=
    'var x := 10; // single-line comment' + LineEnding +
    'var y := 20; (* block comment *)' + LineEnding +
    'var z := x + y; (* multi' + LineEnding +
    'line comment *) writeln(z);';

  OutputStr := StripComments(Input);

  Writeln(OutputStr);
end.



(* run:

var x := 10; 
var y := 20; 
var z := x + y;  writeln(z);

*)

 

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