Re: std::transform for std::map
On Mar 16, 7:46 am, p...@informatimago.com (Pascal J. Bourguignon)
wrote:
Ralf Goertz <r_goe...@expires-2006-11-30.arcornews.de> writes:
it doesn't seem to be possible to use transform for maps.
Yes it is possible:
#include <algorithm>
#include <map>
#include <iterator>
#include <vector>
#include <iostream>
using namespace std;
int doit(std::pair<const int,int>& w) {
return w.second+1;
}
int main() {
map<int,int> m;
map<int,int> o;
m[0]=42;
m[3]=33;
m[6]=66;
m[2]=22;
m[4]=44;
vector<int> v(m.size());
transform(m.begin(),m.end(),v.begin(),doit);
copy(v.begin(),v.end(),ostream_iterator<int>(cout," ")); cout<<en=
dl;
return(0);
}
/*
-*- mode: compilation; default-directory: "/tmp/" -*-
Compilation started at Mon Mar 16 15:45:08
SRC="/tmp/tm.c++" ; EXE="tm" ; g++ -g3 -ggdb3 -o ${EXE} ${SRC} && =
./${EXE} && echo status = $?
43 23 34 45 67
status = 0
Compilation finished at Mon Mar 16 15:45:09
*/>
doesn't help. What would be the right way to do it?
You need to declare the key const in the pair.
Even better would be:
typedef std::map<int, int> intmap;
int doit(intmap::value_type w)
{
return w.second + 1;
}
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