Reading a multimap from a file

Question

I need to read a multimap<int,string> from a file and i can't figure out how to do it.

ifstream in ("words.txt");
multimap<int, string> words;
int count = 0;
while (!in.eof()) {
        getline(in, words[count]);
        count++;
}

When i run it i get this error error: no match for ‘operator[]’ (operand types are ‘std::multimap<int, std::__cxx11::basic_string<char> >’ and ‘int’) getline(in, words[count]); I tried with in >> words[count], and it doesn't work too. How should i fix this ?

Not directly related to your error, but before it bites you : [do not use `eof()` as a loop condition](http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong). — Quentin, May 19 '16 at 13:15
a) dont use while (!in.eof), google it youll find an answer on stackoverflow b) multimap [doesnt seem to have that operator](http://en.cppreference.com/w/cpp/container/multimap) — Borgleader, May 19 '16 at 13:15

score 1 · Accepted Answer · answered May 19 '16 at 13:22

1

The multimap doesn't have operator[].

You can use the insert method of multimap, or emplace if you use C++11.

See here for emplace documentation and example.

answered May 19 '16 at 13:22

Mayhem

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score 0 · Answer 2 · answered May 19 '16 at 13:16

0

Use .insert() method:

cplusplus reference

Also if you want each pair at subsequent index you might want to use std::vector and push_back()

answered May 19 '16 at 13:16

MaciekGrynda

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score 0 · Answer 3 · answered May 19 '16 at 13:16

0

There is no [] operator for std::multimap. You must read a line as a string and then use insert.

answered May 19 '16 at 13:16

Jean-Baptiste Yunès

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Reading a multimap from a file

3 Answers3