delphi - How can i define typed constant and use it in functions argument -

when defined typed constant can't use in default value of functions argument, example:

const   defc   :char  = ',';    function fun(delimiter :char=defc); 

when run code compiler show error :

[dcc32 error] : e2026 constant expression expected 

if not defined type, compiler set type ansichar , bad code, how can use way or way can compiler use char , not use ansichar character constants?

you seem rely little bit on tool-tip information. info not produced actual compiler, , not worth place bets on.

anyway, character , string literals context sensitive. means compiler (actual code generator) create appropriate code depending on how literal used.

consider these 2 consts (as alternatives):

const   defc = ',';     // tool-tip shows system.ansichar   defc = #$0298;  // tool-tip shows system.ansichar here too! 

this shows tool-tip can't relied on here, because doesn't know in context const used.

then consider following 2 functions:

function fun1(delimiter: char = defc): integer; begin   result := ord(delimiter); end;  function fun2(delimiter: ansichar = defc): integer; begin   result := ord(delimiter); end; 

and following onclick handler, calling functions

procedure tmainform.button7click(sender: tobject); begin   showmessage(inttostr(fun1));   showmessage(inttostr(fun2)); end; 

the code produced compiler differs 2 calls

mainformu.pas.233: showmessage(inttostr(fun1)); 00605036 66b89802         mov ax,$0298   // $002c if defc = ',' 0060503a e8a5ffffff       call fun1 ... mainformu.pas.234: showmessage(inttostr(fun2)); 0060504f b098             mov al,$98     // $2c if defc = ',' 00605051 e8a6ffffff       call fun2 ... 

in first call, fun1() requires char, defc literal treated unicode char, #$2098 (or $002c if defc = ',').

in second call, fun2() requires ansichar, defc const treated ansichar, #$98 (or $2c if defc = ',').

iow, character literal context sensitive, stated above.

as side note, worrying no compiler warning issued second call.