[fpc-pascal] ansistrings access by character

[Florian Klaempfl]

L505 wrote:

> |
> | Or if you wanted to prepend exceptions rather than catch them, the following
> | function could also work have worked (note you have to do a shortString cast,
> | AnsiStrings don't like access by character)
> |
> 
> I was under the same impression for a long time, but some of the FPC RTL sources
> use ansistrings and access by character. The findpart function for example uses
> ansistrings but accesses by string[n]
> 
> 
> For example this compiles and runs.
> 
> var
>  test:ansistring;
> function IsANumber (InStr : AnsiString) : Boolean;
> var
>   TempBool: Boolean;
>   Str: ansiString;
>   I: Integer;
> begin
>  Str := InStr;
>  TempBool := True;
>  I := 1;
> 
>  while (I <= Length(Str)) and (TempBool = True) do
>  begin
>   TempBool := Str[I] in ['0'..'9'];
>   Inc(I);
>  end;
>  IsANumber := TempBool
> end;
> 
> begin
>  test:='testing';
>  test[1]:='p';
>  writeln(test);
> 
>  test:='5453tyy';
>  if IsANumber(test) then
>    writeln('yes '+test+' is a number')
>  else
>    writeln('no, '+test+' is not a number');
> 
>  test:='545365';
>  if IsANumber(test) then
>    writeln('yes '+test+' is a number')
>  else
>    writeln('no, '+test+' is not a number');
> 
>  readln;
> 
> end.
> 
> 
> So can someone shed the light? Is it just a rumor that ansistrings shouldn't be
> accessed by character? Only specific situations?

Disadvantage:
- it's slow because it calls unique,i.e. ensures that the reference 
counter is 1