CODEWITHSUNDEEP
c++
Alice Everett
Alice Everett

Reputation: 375

Error initializing C++ map

I have created the following class:

class A{
 public:
 static std::map<std::pair<unsigned, unsigned>, unsigned> var1;
};

std::map<std::pair<unsigned, unsigned>, unsigned> A::var1[std::make_pair(0,0)]=0; //it is used to initialize static variable var1 inside A.

However, when I do so I get the following error:

array bound is not an integer constant before ‘]’ token

Is there some way by which I may initialize var1 with some default values?

Upvotes: 2

Views: 285

Answers (4)

el aurens
el aurens

Reputation: 361

In C++98,you can use a function to inialize your static variable. For example, you can do something like this

typedef std::map<std::pair<unsigned, unsigned>, unsigned> mymap;
mymap init() {
 mymap m;
 m[std::make_pair(0,0)] = 0;
 return m;
}

class A {
 public:
  static mymap var1;
};
mymap A::var1 = init();

If you can use C++11, it is shorter 

std::map<std::pair<unsigned, unsigned>, unsigned> A::var1 = {std::make_pair(std::make_pair(0, 0), 0)};

Upvotes: 0

AntiClimacus
AntiClimacus

Reputation: 1420

With C++11

#include <map>
using namespace std;

map<int, char> m = {{{1, 1}, 2}, {{2, 2}, 3}, ...};

Or use boost.assign.

Upvotes: 2

hivert
hivert

Reputation: 10667

You can't declare your variable and initialize one of its item using A[...]= at the same time.

std::map<std::pair<unsigned, unsigned>, unsigned> A;
A::var1[std::make_pair(0,0)]=0;

should work. If C++11 you can use bracket initialization as

std::map<std::pair<unsigned, unsigned>, unsigned> A = {{{0,0}, 0}};

Upvotes: 3

pts
pts

Reputation: 87271

static std::map<std::pair<unsigned, unsigned>, unsigned> CreatVar1() {
  std::map<std::pair<unsigned, unsigned>, unsigned> var;
  var[std::make_pair(0,0)]=0;
  return var;
}
std::map<std::pair<unsigned, unsigned>, unsigned> A::var1 = CreateVar1();

Or, alternatively, in C++11:

std::map<std::pair<unsigned, unsigned>, unsigned> A::var1 = {{{0, 0}, 0}};

Upvotes: 3

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