C ++ Issue with map and the Compare Class

Question

I was hoping maybe someone could help me solve my issue. I get a lovely

No matching function for call to object of type 'const pCompare'

struct pCompare { bool operator()( const std::string & str1, const std::string & str2 ) const { return str1.compare( str2 ) == 0; } }; std::string *t = new std::string ( "/test.html" ); std::map<std::string*, std::string, pCompare> test; test.insert ( std::pair<std::string*, std::string> ( t, "héhé" ) ); std::cout << test.find(new std::string ("/test.html") )->second;

Thanks for your help !

Your map has (const) string * as keys yet your comparator takes const string &... — Eugen Constantin Dinca
– Eugen Constantin Dinca, Commented Nov 6, 2012 at 22:02
Is it possible to change your implementation to use std::map<std::string, std::string>. Using values instead of pointers can make things a lot easier. — andre
– andre, Commented Nov 6, 2012 at 22:05
Also note that comparators should test for ordering not equality otherwise you go into UB land. — Eugen Constantin Dinca
– Eugen Constantin Dinca, Commented Nov 6, 2012 at 22:13

hege · Accepted Answer · 2012-11-06 22:07:57Z

First of all, do not do this, as it will screw up your map: You need an ordering function for the map, not an equality test.

Anyway, I guess you problem is that your key type std::string* but your function tests for string& . I haven't tried this, but this should do the trick:

bool operator()( std::string * str1, const std::string * str2 ) const { return *str1 < *str2; }

I did forgot the treee part of the map, my bad... In anyway the reference was the issue

Collectives™ on Stack Overflow

C ++ Issue with map and the Compare Class

1 Answer 1

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Related