[boost] [optional] little addition

Subject: [boost] [optional] little addition
From: Arno Schödl (aschoedl_at_[hidden])
Date: 2009-02-27 04:08:23

I just started using boost::optional, and this proved to be generically useful, but I believe is currently not in boost::optional:

template< class T, class Tcompatible >
bool optional_assign( T& t, boost::optional<Tcompatible> const& optt ) {
        if( optt ) {
                t=*optt;
                return true;
        } else {
                return false;
        }
}

so you can write

boost::optional< TMyValue > TryToGetT();
T t;

if( !optional_assign( t, TryToGetT () ) {
    ... other way to get t ...
}

instead of the more verbose:

boost::optional< TMyValue > TryToGetT();
T t;

boost::optional< TMyValue > const& optt=TryToGetT();
if( optt ) {
    t=*optt;
} else {
    ... other way to get t ...
}

get_optional_value_or is similar, but the alternative must be an expression and is eagerly evaluated, both of which may be undesirable.

Arno

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Dr. Arno Schoedl · aschoedl_at_[hidden] 
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