无法让二传手开始工作

Question

The code:

HEADER

class Parser{

private:
    unsigned int cant_documentos;
    unsigned int cant_terminos;
    std::map<std::string,short> dicc_stopwords;
    std::map<std::string,unsigned int> hash_frecuencias_globales;
    std::map<std::string,std::map<std::string,unsigned int> > hash_frecuencias_locales;
    std::map<std::string,std::string> hash_apariciones_unicas;
public:
    Parser();
    ~Parser();


public:
    void setFrecuenciasGlobales(std::map<std::string,std::map<std::string,unsigned int> > frecuencias);
};

END OF HEADER

.CPP

void Parser::setFrecuenciasGlobales(map<string,map<string,unsigned int> > frecuencias){
hash_frecuencias_globales = frecuencias;
cant_terminos = frecuencias.size();
}

END OF CPP

COMPILER OUTPUT:

parser/parser.cpp:102:30: error: no match for ‘operator=’ in ‘((Parser*)this)->Parser::hash_frecuencias_globales = frecuencias’
parser/parser.cpp:102:30: note: candidate is:
/usr/include/c++/4.6/bits/stl_map.h:253:7: note: std::map<_Key, _Tp, _Compare, _Alloc>& std::map<_Key, _Tp, _Compare, _Alloc>::operator=(const std::map<_Key, _Tp, _Compare, _Alloc>&) [with _Key = std::basic_string<char>, _Tp = unsigned int, _Compare = std::less<std::basic_string<char> >, _Alloc = std::allocator<std::pair<const std::basic_string<char>, unsigned int> >, std::map<_Key, _Tp, _Compare, _Alloc> = std::map<std::basic_string<char>, unsigned int>]
/usr/include/c++/4.6/bits/stl_map.h:253:7: note:   no known conversion for argument 1 from ‘std::map<std::basic_string<char>, std::map<std::basic_string<char>, unsigned int> >’ to ‘const std::map<std::basic_string<char>, unsigned int>&’

Where is the problem?

Answer 1

hash_frecuencias_globales is a std::map<std::string,unsigned int> , and you are trying to assign a std::map<std::string,std::map<std::string,unsigned int> > to it:

void Parser::setFrecuenciasGlobales(map<string,map<string,unsigned int> > frecuencias){
  hash_frecuencias_globales = frecuencias; // oops!

As to passing frequencias by value, this would only make sense if you were to move from it, or call std::map::swap . For a simple assignment, it would be better to pass by const reference and avoid unnecessary copies.

Answer 2

freceuncias is a map from string to a map from string to unsigned int :

std::map<std::string, std::map<std::string, unsigned int> > frecuencias

You're trying to assign this into hash_frecuencias_globales , which is a map from string to unsigned int :

std::map<std::string,unsigned int> hash_frecuencias_globales;

That's not possible, hence the error. Perhaps you only wanted to assign only the part of frequencias corresponding to a particular key?

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As a side note (and also pointed out by @RichardPlunkett), you should pass big objects such as maps by const-reference instead of by value if you intend to only inspect them or copy parts of them - this will save a lot of unnecessary copying.

Answer 3

Note the type of frecuencias , it's not the same type of map as hash_frecuencias_globales .

std::map<std::string,unsigned int> hash_frecuencias_globales;
map<string,map<string,unsigned int> > frecuencias