conflicting declaration when filling a static std::map class member variable

I have a class with a static std::map member variable that maps chars to a custom type Terrain. I'm attempting to fill this map in the class's implementation file, but I get several errors. Here's my header file:

#ifndef LEVEL_HPP
#define LEVEL_HPP

#include <bitset>
#include <list>
#include <map>
#include <string>
#include <vector>
#include "libtcod.hpp"

namespace yarl
{
    namespace level
    {
        class Terrain
        {
        // Member Variables
            private:
               std::bitset<5> flags;

        // Member Functions
            public:
                explicit Terrain(const std::string& flg)
                : flags(flg) {}

            (...)
        };



        class Level
        {
            private:
                static std::map<char, Terrain> terrainTypes;

            (...)
        };
    }
}

#endif 

and here's my implementation file:

#include <bitset>
#include <list>
#include <map>
#include <string>
#include <vector>
#include "Level.hpp"
#include "libtcod.hpp"
using namespace std;

namespace yarl
{
    namespace level
    {
        /* fill Level::terr开发者_开发知识库ainTypes */
        map<char,Terrain> Level::terrainTypes['.'] = Terrain("00001");  // clear
        map<char,Terrain> Level::terrainTypes[','] = Terrain("00001");  // clear 
        map<char,Terrain> Level::terrainTypes['\''] = Terrain("00001"); // clear
        map<char,Terrain> Level::terrainTypes['`'] = Terrain("00001");  // clear
        map<char,Terrain> Level::terrainTypes[178] = Terrain("11111");  // wall

        (...)
    }
}

I'm using g++, and the errors I get are

src/Level.cpp:15: error: conflicting declaration ‘std::map, std::allocator > > yarl::level::Level::terrainTypes [46]’

src/Level.hpp:104: error: ‘yarl::level::Level::terrainTypes’ has a previous declaration as ‘std::map, std::allocator > > yarl::level::Level::terrainTypes’

src/Level.cpp:15: error: declaration of ‘std::map, std::allocator > > yarl::level::Level::terrainTypes’ outside of class is not definition

src/Level.cpp:15: error: conversion from ‘yarl::level::Terrain’ to non-scalar type ‘std::map, std::allocator > >’ requested

src/Level.cpp:15: error: ‘yarl::level::Level::terrainTypes’ cannot be initialized by a non-constant expression when being declared

I get a set of these for each map assignment line in the implementation file. Anyone see what I'm doing wrong? Thanks for your help.

You can initialize static members outside of functions, but you can't perform arbitrary operations.

You could use a function to initialize the members:

namespace {
    std::map<char, Terrain> initTerrainTypes() {
        std::map<char, Terrain> m;
        m['.'] = Terrain("00001"); 
        // ...
        return m;
    }
}

map<char,Terrain> Level::terrainTypes = initTerrainTypes();

Or you could use initialization utilities like Boost.Assign:

map<char,Terrain> Level::terrainTypes = boost::assign::map_list_of
   ('.', Terrain("00001"))
   // ...
   (178, Terrain("11111"));