c++ - libreria - Usando la matriz como valor de mapa: no se puede ver el error

map programacion

Question

Estoy intentando crear un mapa, donde la clave es un int, 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, aparece 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

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

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 . Puedes usar boost::array o std::vector .

Answer 3

No asigne a un int [], en su lugar, asigne a un int * como este:

#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 4

No puedes copiar matrices por valor así.

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

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

2) Usa un mapa de punteros a 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) Utilice tuplas de refuerzo en lugar de matrices de 3 elementos.

4) En lugar de usar una matriz, cree una nueva estructura que tome 3 elementos. Hacer 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 5

Otra alternativa es colocar los arreglos en una estructura de 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 6

Utilice 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

Enfoque usando 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));