[fpc-pascal] ansistrings access by character

[L505]

|
| 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?