Re: [boost] whitespace and user-defined types in lexical_cast

From: Alexander Nasonov (alnsn_at_[hidden])
Date: 2007-01-28 13:52:54

john_at_[hidden] wrote:
> 
> I am having some trouble with lexical_cast that I think illustrates
> a problem with the underlying implementation.  My basic
> problem is that I'd like lexical_cast to "work" for user-defined
> types (UDTs) that conform to lexical_cast's documented specification of
> OutputStreamable, InputStreamable, CopyConstructible and
> DefaultConstructible.
[ skiped ]

> std::istream& operator>>(std::istream& s, Udt& u){
>     return s >> u.a >> u.b;
> }

I believe that this implementation is incorrect. If you put a writespace
in output operator, you should be prepared for skipws flag and read the
writespace explicitly:

std::istream& operator>>(std::istream& s, Udt& u){
    s >> u.a;
    if((s.flags() & std::ios_base::skipws) == 0)
    {
        char whitespace;
        s >> whitespace;
    }
    return s >> u.b;
}

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Alexander Nasonov
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