[fpc-devel] ThousandSeparator

[Hans-Peter Diettrich]

Mattias Gaertner schrieb:

> Does concatenating a string and a WideChar create a UnicodeString? Can
> this become a problem?

Concatenation requires 2 strings, so everything depends on the concrete 
code. Regardless of eventual compiler magics, something like this will 
happen:

var c: WideChar; s, cs: string;
cs := c; //dunno if accepted by the compiler
s := s + cs;

The WideChar can be converted into an Unicode (UTF-8 or UTF-16) string. 
Afterwards this string may need another conversion, when the other 
string has a different encoding. In the worst case *both* strings are 
converted to the default Unicode representation (Delphi: UTF-16, 
Lazarus: UTF-8?), before they are concatenated. Another conversion may 
occur when the resulting string is assigned to a variable.

All this may become simpler when CP_ACP is used (at least in Delpi), and 
the separator is given in that encoding, as a single byte/AnsiChar in 
case of an SBCS CP_ACP. When Lazarus instead uses UTF-8 (MBCS) for 
CP_ACP, the character occupies more than one byte, so that this 
simplification is impossible. This suggests to store the delimiter as an 
string, instead of a WideChar, whereupon a concatenation of the strings 
may not require any further conversion.

Finally, when the expression (s+cs) is of type RawByteString (depending 
on the involved function declarations), the result will be stored in the 
target variable *without* another conversion. Then the static and 
dynamic encoding of s may be different afterwards.

DoDi