Subject: Re: [Boost-users] if_then_else_return (boost::lambda) question
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2009-02-18 21:38:44
AMDG
Jonathan Leonard wrote:
> I'm fairly new to boost and have a little problem with
> if_then_else_return. Can anyone tell me the problem with the following
> short program? [It seems that my 'thenBranch' and 'elseBranch'
> functions are never called and if_then_else_return' always returns
> true (as if the 'then' branch were called)].
The problem is that Boost.Lambda doesn't automatically call the
boost::function.
Thus, evaluating the lambda expression returns a boost::function,
boost::function
implicitly converts to bool. (false iff the boost::function is empty.)
If you use boost::lambda::bind(MakeReturnTrue(thenBranch)), it should work.
> P.S. (A more general C++ q: A little improvement I'd like to make is
> to drop the ITERATORTYPE type argument from IfNotEndThenElseReturn and
> use CONTAINERTYPE::iterator instead, but the compiler won't allow
> that. Anyone know why?). Thanks again!
typename CONTAINERTYPE::iterator works for me. Did you forget
typename?
In Christ,
Steven Watanabe