'hash_map'未在此范围中使用g ++ 4.2.1声明 [英] 'hash_map' was not declared in this scope with g++ 4.2.1

问题描述

我想使用sgi hash_map。

I am trying to use sgi hash_map.

#include <list>
#include <iostream>
#include <string>
#include <map>
#include <cstring>
#include <tr1/unordered_map>
#include <ext/hash_map>


using namespace std;
struct eqstr
{
  bool operator()(const char* s1, const char* s2) const
  {
    return strcmp(s1, s2) == 0;
  }
};


int main()
{
  hash_map<const char*, int, hash<const char*>, eqstr> months;

  months["january"] = 31;
  months["february"] = 28;
  months["march"] = 31;
  months["april"] = 30;
  months["may"] = 31;
  months["june"] = 30;
  months["july"] = 31;
  months["august"] = 31;
  months["september"] = 30;
  months["october"] = 31;
  months["november"] = 30;
  months["december"] = 31;

  cout << "september -> " << months["september"] << endl;
  cout << "april     -> " << months["april"] << endl;
  cout << "june      -> " << months["june"] << endl;
  cout << "november  -> " << months["november"] << endl;
} 

on gcc4.2我收到错误

on gcc4.2 I am getting the error

listcheck.cc: In function 'int main()':
listcheck.cc:22: error: 'hash_map' was not declared in this scope
listcheck.cc:22: error: expected primary-expression before 'const'
listcheck.cc:22: error: expected `;' before 'const'
listcheck.cc:24: error: 'months' was not declared in this scope

/ p>

while the same code compile with 3.4.

推荐答案

包含文件< ext / hash_map> a href =http://www.aoc.nrao.edu/~tjuerges/ALMA/STL/html/ext_2hash__map.html> GNU扩展哈希映射类，并在命名空间中声明 __ gnu_cxx 。您可以显式限定模板名称或添加：

The include file <ext/hash_map> refers to the GNU extension hash map class and this is declared in namespace __gnu_cxx. You can either explicitly qualify the template name or add:

using namespace __gnu_cxx;

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