Initialization of a hash_map in C++

Question

I've created a map in C++ to store directions for different chess pieces using the following structure:

map<Piece, vector<tuple<Offset, Type, Color>>> PIECE_DIRECTIONS;

When attempting to add elements to the map, such as:

PIECE_DIRECTIONS[Pawn].push_back(tuple<Up, Push, Red>);
PIECE_DIRECTIONS[Soldier].push_back(tuple<Up, Push, Red>);

I'm getting the error message 'This declaration has no storage class or type specifier.' How can I resolve this issue? Are there alternative ways to achieve the same goal, such as using vectors or arrays instead of a map?

Is accessing elements in a map faster compared to arrays and vectors? In my specific case, the speed of accessing elements is crucial, and methods like insertions and deletions are not a significant consideration.

Answer 1

You will get something like this (I did not add the vector yet, but that adds on level of extra {} for initialization). I just wanted to give you an idea. ;)

#include <string>
#include <map>

enum class Piece
{
    Pawn,
    Bishop,
    Rook
};

enum class Color
{
    Black,
    White
};

struct Direction
{
    int horizontal;
    int vertical;
};

struct Movement
{
    Color color;
    Direction direction;
};

int main()
{
    std::map<Piece,Movement> moves{
        { Piece::Pawn, // <- key of your map, e.g. a Piece enum value
         { 
            Color::White,   // First member of Movement, e.g. Color enum value
            {0,1}           // Second member of Movement, Direction {0 horizontal, 1 vertical)
         }
        },
        { Piece::Bishop, { Color::Black, {8,8} } }
    };

    return 0;
}