Passing a char array by value

Question

I have problem with passing a char array by value to a priority_queue. I want to pass a unique value to the constructor, but I can only assign the type in the priority queue to char*. This causes a problem since the value passed changes through each iteration in the algorithm and then all the values in the priority queue (since every element is a pointer to task). Here is a code sample:

 char task[100];
 char priority;
 pair<int, char*> temp;
 priority_queue< int, vector<pair<int, char*>>, compare> queue;
 printf("Define a priority and a task to be done (exit by pressing CTRL-D):\n\n");
 do {
    priority=getchar();
    if(isdigit(priority)){
      scanf("%s", task);
      temp=make_pair(atoi(&priority), task); //I want to pass by value here not by reference, is there any solution to this?
      queue.push(temp);
      printf("%i %s\n", temp.first, temp.second);
    }
 } while(priority != EOF);

Is there any way that I can assign a unique string to every element of the priority queue?

The C++ solution: pass a string or vector<char> by value. The C solution: struct foo { char task[100]; }; and pass that struct by value. — user529758
– user529758, Commented Aug 5, 2013 at 13:31
Just use make_pair(..., std::string(task)) and change the related types accordingly. — Jon
– Jon, Commented Aug 5, 2013 at 13:33
Ok. I get it, this is a solution to the problem. Using char[] only is not a option at all in this case? — user1319951
– user1319951, Commented Aug 5, 2013 at 13:39

MAnyKey · Accepted Answer · 2013-08-06 08:35:47Z

2

As comment to question suggests you can wrap char [100] and int to new type (since pair<> gives poor abstraction). Another option is to use std::string, std::vector<char>, std::array<char, 100> instead of char[100].

PS: call to atoi(&priority) might fall because atoi expects null-terminated C-string, not a pointer to single character.

edited Aug 6, 2013 at 8:35

answered Aug 5, 2013 at 13:48

MAnyKey

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Comments

Useless · Accepted Answer · 2013-08-05 13:49:38Z

0

You could use something like std::array<char,100> I guess, but your current vector type requires a dynamically allocated string.

Do you want to force every element of your vector to be more than 100 bytes, however long the string?

answered Aug 5, 2013 at 13:49

Useless

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