Re: STL algorithm member function problem

From:
Alberto Ganesh Barbati <AlbertoBarbati@libero.it>
Newsgroups:
comp.lang.c++.moderated
Date:
16 Nov 2006 05:23:05 -0500
Message-ID:
<75W6h.44630$Fk1.88241@twister2.libero.it>
Markus Moll ha scritto:

1. remove_if is not doing what you think it does. remove_if(b,e,pred)
returns an iterator k such that the range [b,k) contains those elements x
for which pred(x) is false. Nevertheless, no elements are actually removed
from the underlying container (you couldn't, only given the iterators. And
maybe you couldn't at all. Consider int arr[42] }

2. ptr_fun is not doing what you think it does. It is just a wrapper around
ordinary pointers to functions, so that you suddenly have the member
typedefs argument_type and result_type. The predicate you are looking for
is *ruleIter.

Correcting both, we get:

vector<string>::iterator current_end = fileList.end();
for(vector<RulePtr>::const_iterator ruleIter = m_rules.begin();
    ruleIter != m_rules.end(); ++ruleIter) {

    current_end = std::remove_if(fileList.begin(), current_end, *ruleIter);
}


This code is not doing what you think it does ;-) It suffers the slicing
problem. In fact it won't even compile because Rule is an abstract
class, which can't be passed by-value, but would it be incorrect
regardless of that. See my other post for details.

Ganesh

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