I'm having trouble using bind1st with mem_fun1. I can't compile
the line marked below with a @@. If I use the join2 method everything
is fine, but I wind up passing string vectors by value. I would like
to use the reference passing version, or something similar.
The errors I get point the finger at binder1st::oper ator() being defined
as "const argument_type&" which becomes "const const string_vector&& "
when i use Joiner::join below.
Any advice would be appreciated. I use vc7.1
#include <string>
#include <vector>
#include <functional>
#include <algorithm>
#include <numeric>
#include <iostream>
typedef std::basic_stri ng<char> string;
typedef std::vector<str ing> string_vector;
struct Joiner {
string join (const string_vector& v) {
return std::accumulate (v.begin(), v.end(), string()); }
string join2 (string_vector v) {
return std::accumulate (v.begin(), v.end(), string()); }
};
int main (int argc, char** argv)
{
// a 10x7 matrix of strings initialized to "Text"
std::vector<str ing_vector> vv (10, string_vector (7, "Text"));
Joiner j;
string_vector result (vv.size());
std::transform (vv.begin(), vv.end(),
result.begin(),
//std::bind1st (std::mem_fun1 (&Joiner::join) , &j)); //error
std::bind1st (std::mem_fun1 (&Joiner::join2 ), &j));
std::copy (result.begin() , result.end(),
std::ostream_it erator<string> (std::cout, "\n"));
return 1;
} 1 5801
* pillbug: I'm having trouble using bind1st with mem_fun1. I can't compile the line marked below with a @@. If I use the join2 method everything is fine, but I wind up passing string vectors by value. I would like to use the reference passing version, or something similar.
The errors I get point the finger at binder1st::oper ator() being defined as "const argument_type&" which becomes "const const string_vector&& " when i use Joiner::join below.
Any advice would be appreciated. I use vc7.1
#include <string> #include <vector> #include <functional> #include <algorithm> #include <numeric> #include <iostream>
Pedantic: #include <ostream> here (not that your compiler will complain).
typedef std::basic_stri ng<char> string;
Please don't define a name that's used by the standard library; it only
sows confusion, and acts as a bug-attractor.
typedef std::vector<str ing> string_vector;
Good.
struct Joiner { string join (const string_vector& v) { return std::accumulate (v.begin(), v.end(), string()); } string join2 (string_vector v) { return std::accumulate (v.begin(), v.end(), string()); } };
Is there perhaps some reason why these functions are non-const member
functions? I'll assume there is. But in the context of the code you've
shown, there's none: they should at least be const, preferably static,
or perhaps non-member.
int main (int argc, char** argv) { // a 10x7 matrix of strings initialized to "Text" std::vector<str ing_vector> vv (10, string_vector (7, "Text"));
Joiner j; string_vector result (vv.size()); std::transform (vv.begin(), vv.end(), result.begin(), //std::bind1st (std::mem_fun1 (&Joiner::join) , &j)); //error std::bind1st (std::mem_fun1 (&Joiner::join2 ), &j));
std::copy (result.begin() , result.end(), std::ostream_it erator<string> (std::cout, "\n"));
return 1;
That's an undefined return value, but in practice it maps to "error".
You'd want to indicate "success". Do that by omitting return, or by
returning 0 (which is the default for main), or EXIT_SUCCESS.
}
Regarding the error, try
class JoinerFunc: public std::unary_func tion<string_vec tor, string>
{
private:
Joiner* myJ;
public:
JoinerFunc( Joiner* j ): myJ( j ) {}
string operator()( string_vector const& v ) const
{ return myJ->join( v ); }
};
int main()
{
// a 10x7 matrix of strings initialized to "Text"
std::vector<str ing_vector> vv (10, string_vector (7, "Text"));
Joiner j;
string_vector result (vv.size());
std::transform(
vv.begin(), vv.end(), result.begin(), JoinerFunc( &j )
);
std::copy (result.begin() , result.end(),
std::ostream_it erator<string> (std::cout, "\n"));
}
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail? This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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