C ++中的调用函数

Question

I'm trying to call a function with no return type but it doesn't seem to be getting called.

The code looks something like this(summarized):

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

int ItemsInQuestion[4];

void GetQuestions(int NumQuests);


int main()
{
    int NumberOfQuestions = 0;
    srand((unsigned)time(NULL));
    cout << "How many questions would you like?" << endl;
    cin >> NumberOfQuestions;
    cout << NumberOfQuestions << " questions will be asked.";
    GetQuestions(NumberOfQuestions);
    system ("PAUSE");
    return 0;

}

void GetQuestions(int NumQuests)
{
    for(int Questions=NumQuests; Questions>NumQuests; Questions++)
    {
        ItemsInQuestion[0]=(rand()%(263))+1;
        ItemsInQuestion[1]=(rand()%(263))+1;
        ItemsInQuestion[2]=(rand()%(263))+1;
        ItemsInQuestion[3]=(rand()%(263))+1;
        cout << ItemsInQuestion[0] << ' ' << ItemsInQuestion[1] << ' ' <<ItemsInQuestion[2] << ' ' << ItemsInQuestion[3];
    }
}

The line that outputs the values in the array never comes up. What is causing this?

Answer 1

Because

 int Questions=NumQuests; 

and

 Questions>NumQuests;

don't like each other.

You set Questions to NumQuests and then tell the loop to keep going as long as Questions is strictly greater than NumQuests , which it isn't to start off with.

Even if it was, you'd soon run into an overflow and undefined behavior .

Answer 2

This is not the way of using for-loops :

for ( __Initialization, __Condition, __Increment)

As Grigore pointed out in his answer, your initialization is wrong. As Questions=NumQuest , the statement Questions>NumQuests is false from the beginning, and your code is equivalent to

for ( ; 1<1 ; ) // I'm a lazy loop, I'm ugly and useless

There is an infinite number of way to do what you want :

// Direct : 0, 1, 2, .. NumQuest-1.
for (int Questions=0 ; Questions < NumQuests ; Questions++) 
{ ... } 
// Reverse : NumQuest, ..., 2, 1.
for (int Questions=NumQuests ; Questions > 0 ; Questions--)
{ ... }