Char and Chr in Delphi

char, delphi

Solution

I did a small test in D2007:

program CharChr;

{$APPTYPE CONSOLE}

uses
  Windows;

function GetSomeByte: Byte;
begin
  Result := Random(26) + 65;
end;

procedure DoTests;
var
  b: Byte;
  c: Char;
begin
  b := GetSomeByte;
  IsCharAlpha(Chr(b));
  b := GetSomeByte;
  IsCharAlpha(Char(b));

  b := GetSomeByte;
  c := Chr(b);
  b := GetSomeByte;
  c := Char(b);
end;

begin
  Randomize;
  DoTests;
end.

Both calls produce the same assembly code:

CharChr.dpr.19: IsCharAlpha(Chr(b));
00403AE0 8A45FF           mov al,[ebp-$01]
00403AE3 50               push eax
00403AE4 E86FFFFFFF       call IsCharAlpha
CharChr.dpr.21: IsCharAlpha(Char(b));
00403AF1 8A45FF           mov al,[ebp-$01]
00403AF4 50               push eax
00403AF5 E85EFFFFFF       call IsCharAlpha

CharChr.dpr.24: c := Chr(b);
00403B02 8A45FF           mov al,[ebp-$01]
00403B05 8845FE           mov [ebp-$02],al
CharChr.dpr.26: c := Char(b);
00403B10 8A45FF           mov al,[ebp-$01]
00403B13 8845FE           mov [ebp-$02],al

Edit: Modified sample to mitigate Nick's concerns.

Edit 2: Nick's wish is my command. ;-)

Problem

The difference between Chr and Char when used in converting types is that one is a function and the other is cast So: `Char(66) = Chr(66)` I don't think there is any performance difference (at least I've never noticed any, one probably calls the other).... I'm fairly sure someone will correct me on this! EDIT Thanks to Ulrich for the test proving they are in fact identical. EDIT 2 Can anyone think of a case where they might not be identical, e.g. you are pushed towards using one over the other due to the context? Which do you use in your code and why?

Original source