Greg Buchholz wrote:[color=blue]
> I'm wondering if anyone has advice for figuring out error messages
> produced by g++. The programs below works fine, until I uncomment out
> the two "transform" lines. Then it points me to line 24 (where the
> second "bind1st" is) and results in an error message complaining about
> no match for 'operator=' and/or problems with 'back_insert_iterator'
> (see the entire error message reproduced below). Do I need a cast
> somewhere to keep the type-checker happy? Is it a template problem?
> Since I'm working with standard containers, I can't imagine that
> there's no assignment operator defined. Is there a subtle mistake I've
> made, or am I doing something obviously wrong? In addition to figuring
> out this particular error, I'd also appreciate general strategies for
> figuring out compiler messages produces by g++. Do commercial products
> do a better job in the error message department?
>
> Thanks,
>
> Greg Buchholz[/color]
I'm with you that the error messages involving STL classes can be pretty
hard to parse. The problem in your case is that the function aux
returns a list<string> and your output iterator in transform,
back_inserter(out), expects to receive strings. It's writing them
*into* a list of strings, but the things being written need to be strings.
Changing the definition of out to, for example:
list<list<string> > out;
will produce compilable code.
-Mark
[color=blue]
>
>
> #include <list>
> #include <string>
> #include <iostream>
> #include <algorithm>
> #include <iterator>
> #include <functional>
>
> using namespace std;
>
> list<string> aux(list<string> ps, string n);
>
> int main()
> {
>
> list<string> f, out;
>
> f.push_back("foo");
> f.push_back("bar");
> f.push_back("baz");
>
> list<string> g = bind1st(ptr_fun(*aux),f)("TEST");
>
> //transform(f.begin(),f.end(),back_inserter(out),
> // bind1st(ptr_fun(aux),f));
>
> copy(g.begin(),g.end(),ostream_iterator<string>(co ut, " "));
> cout << endl;
>
> return 0;
> }
>
> list<string> aux(list<string> ps, string n)
> {
> list<string> out;
> transform(ps.begin(),ps.end(),back_inserter(out),
> bind1st(plus<string>(),n));
> return out;
> }
>
>
> /usr/local/lib/gcc/i686-pc-linux-gnu/3.4.2/../../../../include/c++/3.4.2/bits/stl_algo.h:
> In function `_OutputIterator std::transform(_InputIterator,
> _InputIterator, _OutputIterator, _UnaryOperation) [with _InputIterator
> =
> std::_List_iterator<std::string>, _OutputIterator =
> std::back_insert_iterator<std::list<std::string,
> std::allocator<std::string> > >, _UnaryOperation =
> std::binder1st<std::pointer_to_binary_function<std ::list<std::string,
> std::allocator<std::string> >, std::string, std::list<std::string,
> std::allocator<std::string> > > >]': test3.cpp:24: instantiated from
> here
> /usr/local/lib/gcc/i686-pc-linux-gnu/3.4.2/../../../../include/c++/3.4.2/bits/stl_algo.h:789:
> error: no match for 'operator=' in
> '(&__result)->std::back_insert_iterator<_Container>::operator * [with
> _Container = std::list<std::string, std::allocator<std::string> >]() =
> std::binder1st<_Operation>::operator()(typename
> _Operation::second_argument_type&) const [with _Operation =
> std::pointer_to_binary_function<std::list<std::str ing,
> std::allocator<std::string> >, std::string, std::list<std::string,
> std::allocator<std::string> >
>[color=green]
>>](((std::string&)(+(&__first)->std::_List_iterator<_Tp>::operator*[/color]
>
> [with _Tp = std::string]())))'
> /usr/local/lib/gcc/i686-pc-linux-gnu/3.4.2/../../../../include/c++/3.4.2/bits/stl_iterator.h:363:
> note: candidates are: std::back_insert_iterator<_Container>&
> std::back_insert_iterator<_Container>::operator=(t ypename
> _Container::const_reference) [with _Container = std::list<std::string,
> std::allocator<std::string> >]
> /usr/local/lib/gcc/i686-pc-linux-gnu/3.4.2/../../../../include/c++/3.4.2/bits/stl_iterator.h:338:
> note: std::back_insert_iterator<std::list<std::string,
> std::allocator<std::string> > >&
> std::back_insert_iterator<std::list<std::string,
> std::allocator<std::string> > >::operator=(const
> std::back_insert_iterator<std::list<std::string,
> std::allocator<std::string> > >&)
>[/color]
