Re: [Boost-users] Boost Format: format strings and character types

From: Daniel James (gmane.junk001_at_[hidden])
Date: 2008-01-30 13:10:00

In article 
<7253f6b30801300934j29aa2c09ib5c07256a50a38ff_at_[hidden]>, Chun 
ping wang wrote:
> I think the first one won't work because %d is for decimal printing
> , and char is a character.

Well ... yes, that's right. char is a character, and what I want to do 
is to print its decimal value. We're using a char here as an 8-bit int 
not to hold a character.

> Format is a typesafe library so the document should say any type
> safe format will work in here as in printf.

char to int is a safe conversion ... the documentation leads me to 
expect that it will work in format the same way as it does in printf, 
but it doesn't.

The question is: is the code wrong, or is the documentation misleading?

> Instead this would.
>  printf( "Using printf: ii=%d, cc=%d\n", ii, cc );
>  cout << boost::format( "Using boost::format: ii=%1d%, cc=%2d%" ) %
>      ii % cc << endl;

No: %2d$ gives exactly the same as %2% or %d. The only workaround I've 
found is to cast the char variable to int.

Cheers,
 Daniel