Thread: declaring an array of n elements based on input

  1. #1
    Registered User
    Join Date
    Nov 2001

    declaring an array of n elements based on input

    the compiler complains about an integral constant for the array declaration.

    can it be done like this or do i have to use a pointer to set up the array ?

    i know this code is absolutely useless but i'd like to know for theoretical purposes.

    void create(const int);

    int size;

    cin << "Enter a number: " << size;


    return 0;

    void create(const int max)
    int array1[max];


  2. #2
    Registered User
    Join Date
    Sep 2001
    first error you have is your input/output. use cin >> only for input and cout<< for output

    cout<< "Enter a number: ";
    cin >> size;

    second error your function decleration does not match your function. change it to this:

    void create(const int max);

    the program with these changes will work, but the array will not be accessable from main, unless you declare the array in main. then you can pass a pointer or a reference of the array to the function.

  3. #3
    of Zen Hall zen's Avatar
    Join Date
    Aug 2001
    You can't have a static array based on a variable number of elements in standard C++ (it must be a compile time constant). Here are a couple of alternatives -

    #include <vector>
    #include <iostream>
    using namespace std;
    int main() 
    	int size; 
    	cout<< "Enter a number: ";
    	cin >> size; 
    	int* array1 = new int[size];
    	// do stuff
    	delete [] array1;
    	vector<int> array2(size);
    	return 0; 

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