matriz como valor del mapa: no se puede ver el error

Question

Estoy intentando crear un mapa, donde la clave es un entero, y el valor es una matriz

int red[3] = {1,0,0}; 
int green[3] = {0,1,0}; 
int blue[3]  = {0,0,1}; 

    std::map<int, int[3]> colours; 

colours.insert(std::pair<int,int[3]>(GLUT_LEFT_BUTTON,red)); //THIS IS LINE 24 ! 
colours.insert(std::pair<int,int[3]>(GLUT_MIDDLE_BUTTON,blue)); 
colours.insert(std::pair<int,int[3]>(GLUT_RIGHT_BUTTON,green)); 

Sin embargo, cuando intento compilar este código, me sale el siguiente error.

g++ (Ubuntu 4.4.1-4ubuntu8) 4.4.1 

In file included from /usr/include/c++/4.4/bits/stl_algobase.h:66, 
       from /usr/include/c++/4.4/bits/stl_tree.h:62, 
       from /usr/include/c++/4.4/map:60, 
       from ../src/utils.cpp:9: 
/usr/include/c++/4.4/bits/stl_pair.h: In constructor ‘std::pair<_T1, _T2>::pair(const _T1&, const _T2&) [with _T1 = int, _T2 = int [3]]’: 
../src/utils.cpp:24: instantiated from here 
/usr/include/c++/4.4/bits/stl_pair.h:84: error: array used as initializer 
/usr/include/c++/4.4/bits/stl_pair.h: In constructor ‘std::pair<_T1, _T2>::pair(const std::pair<_U1, _U2>&) [with _U1 = int, _U2 = int [3], _T1 = const int, _T2 = int [3]]’: 
../src/utils.cpp:24: instantiated from here 
/usr/include/c++/4.4/bits/stl_pair.h:101: error: array used as initializer 
In file included from /usr/include/c++/4.4/map:61, 
       from ../src/utils.cpp:9: 
/usr/include/c++/4.4/bits/stl_map.h: In member function ‘_Tp& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const _Key&) [with _Key = int, _Tp = int [3], _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, int [3]> >]’: 
../src/utils.cpp:30: instantiated from here 
/usr/include/c++/4.4/bits/stl_map.h:450: error: conversion from ‘int’ to non-scalar type ‘int [3]’ requested 
make: *** [src/utils.o] Error 1 

Realmente no puedo ver dónde está el error. O incluso si hay un error.

Answer 1

No puede copiar matrices por un valor como ese.

Aquí hay varias soluciones, pero me recomiendan # 4 para sus necesidades:

1) utilizar un std::vector lugar de una matriz

2) Utilizar un mapa de punteros a las matrices de 3 elementos.

int red[3] = {1,0,0}; 
int green[3] = {0,1,0}; 
int blue[3]  = {0,0,1}; 
std::map<int,int(*)[3]> colours; 
colours.insert(std::pair<int,int(*)[3]>(GLUT_LEFT_BUTTON,&red)); 
colours.insert(std::pair<int,int(*)[3]>(GLUT_MIDDLE_BUTTON,&blue)); 
colours.insert(std::pair<int,int(*)[3]>(GLUT_RIGHT_BUTTON,&green)); 
//Watch out for scope here, you may need to create the arrays on the heap. 

3) Usar boost tuples en vez de matrices de 3 elementos.

4) En lugar de usar una matriz, crea una nueva estructura que tome 3 elementos. Haz el mapa O envuelva su matriz en una estructura y eso también funcionará.

struct Triple 
{ 
    int color[3]; 
}; 

//Later in code 
Tripple red = {1, 0, 0}, green = {0, 1, 0}, blue = {0, 0, 1}; 
std::map<int,Triple> colours; 
colours.insert(std::pair<int,Triple>(GLUT_LEFT_BUTTON,red)); 
colours.insert(std::pair<int,Triple>(GLUT_MIDDLE_BUTTON,blue)); 
colours.insert(std::pair<int,Triple>(GLUT_RIGHT_BUTTON,green)); 

Answer 2

Las matrices no son construcciones de primera clase en C++. No son Copy Constructible ni Assignable que son requisitos para los valores de std::map. Puede usar boost::array o std::vector.

Answer 3

Arrays no pueden ser los datos almacenados en un contenedor estándar (std::pair)

Answer 4

Otra alternativa es poner las matrices en un struct envoltura:

struct Wrapper { int value[3]; }; 

    // ... 
    Wrapper red = {{1,0,0}};  
    std::map<int,Wrapper> colours;  
    colours.insert(std::pair<int,Wrapper>(1, red)); 

Answer 5

uso std :: make_pair:

int red[3] = {1,0,0}; 
int green[3] = {0,1,0}; 
int blue[3]  = {0,0,1}; 
std::map<int,int(*)[3]> colours; 
colours.insert(std::make_pair(GLUT_LEFT_BUTTON,&red)); 
colours.insert(std::make_pair(GLUT_MIDDLE_BUTTON,&blue)); 
colours.insert(std::make_pair(GLUT_RIGHT_BUTTON,&green)); 

Answer 6

Use std::tr1::array.

typedef std::tr1::array<int, 3> Triple; 
Triple red = {1, 0, 0}; 
Triple green = {0, 1, 0}; 
Triple blue = {0, 0, 1}; 
std::map<int, Triple> colours; 
colours.insert(std::make_pair(GLUT_LEFT_BUTTON, red)); 
colours.insert(std::make_pair(GLUT_MIDDLE_BUTTON, blue)); 
colours.insert(std::make_pair(GLUT_RIGHT_BUTTON, green)); 

Answer 7

no se asignan a un int [], en cambio, asigne a un int * así:

#include <iostream> 
#include <map> 
using namespace std; 
int main(){ 
    std::map<int,int*> colors; 
    int red[] = {3,7,9}; 
    colors[52] = red; 
    cout << colors[52][1]; //prints 7 
    colors[52][1] = 11; 
    cout << colors[52][1]; //prints 11 
    return 0; 
} 

Answer 8

Aproximación utilizando la estructura en C++

int MAX_DATA_PER_INSTR = 8; 
//struct to hold the values. remember to write the constructor 
struct InstrChar 
{ 
    InstrChar(int in[MAX_DATA_PER_INSTR]) { 
    //c alternative is memcopy 
    std::copy(in, in+MAX_DATA_PER_INSTR, data); 
    } 
    int data[MAX_DATA_PER_INSTR]; 
}; 

// create a key value pair 
std::map <int, InstrChar> address_instructions; 
std::map <int, InstrChar>::iterator it; 

// sample array, 8 elements 
int xp[MAX_DATA_PER_INSTR ] = {31,4,3,4,4,3,1,2}; 
address_instructions.insert(std::pair<int, InstrChar>(PC, xp)); 
it = address_instructions.find(PC); 
InstrChar buf1 = it->second; 
//integer pointer to the array, can be dereferenced as *p, *(p+1), .... //*(p+7) 
int *p = buf1.data; 

//in case you need to print these values out. They can also be referred to as buf1.data[0], buf1.data[1], buf1.data[2] 
printf("%d\n", (*p)); 
printf("%d\n", *(p+1)); 
printf("%d\n", *(p+2)); 
printf("%d\n", *(p+3)); 
printf("%d\n", *(p+4)); 
printf("%d\n", *(p+5)); 
printf("%d\n", *(p+6)); 
printf("%d\n", *(p+7));