[boost] Why don't lambda funcs work for stl function objects?

From: Neal D. Becker (ndbecker2_at_[hidden])
Date: 2004-05-13 15:32:54

Any reason lambda functions can't meet requirements for std::unary_function,
for example?  Specifically, it seems result_type is not defined.

For example boost::constant(0) doesn't have result_type, so can't be used
where a std::unary_function is needed.