I have a problem with the following statement: return std::accumulate( qrun_.begin(), qrun_.end(), svt, _1 < if_then_else_return( _2 != (acct*)0, bind(&acct::get_avt, _2), (unsigned)-1)); Basically, I want to find the minimal value of get_avt() over all non-null members of qrun_ which is declared as std::vector. I get the following compiler error with SunCC 5.9: Error, badbinaryop: The operation "unsigned>" is illegal. The get_avt method is declared as: unsigned get_avt() const Removing the const qualifier doesn't help. Replacing (unsigned)-1 with _1 generates the same error, but with "const unsigned" replaced by "unsigned&". Replacing (unsigned)-1 with bare 0 compiles without any error, but does not compute what I want. Any suggestions about what am I doing wrong?