C++ while loops and for loops not working

Question

First, I'll send the code.

    #include <iostream>

using namespace std;

int main() {

  int times = 0;
  cout << "Enter a number of candies:";
  int number;
  cin >> number;

  while (number >= 1000) {
    cout << "Please enter an integer number between 0 and 999.\n";
    cin >> number;

  }


  for (times <= 10; times++; number--) {
    cout << "nomnom I have" << number - 1 << "candies left.\n";
   }




}

I am trying to practice c++ because I'm a beginner so I made a little program that is supposed to allow you to enter a number between 1 and 999, then this is gonna be the number of candies. Then, it says how many there are left. It's not working though. Can anyone tell me why? Thanks.

The first time the for loop is evaluated `times` is 0, so it is not entered. The `times <= 10` part doesn't do anything. — Retired Ninja, Dec 05 '19 at 23:57

bhristov · Answer 1 · 2019-12-06T00:12:09.693

You should have your for loop formatted like this:

  for (; times <= 10; times++, number--) {
    cout << "nomnom I have" << number - 1 << "candies left.\n";
   }

The format of the for loop follows the following rule:

for(<initializer, which you can skip> ; <condition for execution which is required> ; <increment or decrement of the variable which you are bounding with the condition, this part is not required either>)

Within the initializer part you can create multiple variables, you just need to separate them with a ",", the same rule applies to the final part of the for loop. Neither the initializer not the modifier at the end are required for correct syntax. This is a valid example:

int i = 0;
for(; i < 5;)
{
   ++i;
}

For example:

for(int i = 0, j = 5; i < 5 && j > 0; ++i, --j){}

int i = 0, j = 5;
for(; i < 5 && j > 0; ++i, --j){}

int i = 0, j = 5;
for(; i < 5 && j > 0;){
  ++i;
  --j;
}

All of these examples are accomplishing the same task of incrementing i and decrementing j.

Gaben · Answer 2 · 2019-12-06T00:16:56.653

Your for loop is incorrect - it should be done according to this:
for( <initialization> ; <checking> ; <run_in_each_loop> ){ ...}

You can read more about for loop here.

You want your code to do 2 "increments" (<run_in_each_loop>). You can't do this using ; in between

A common idiom is to use the comma operator which evaluates both operands, and returns the second operand. Thus:

for(int i = 0; i != 5; ++i,++j) do_something(i,j);

read more here.

Other way would be to put number-- inside of { ... } brackets.

In the end, your code should look like that:

#include <iostream>
using namespace std;

int main() {

  int times = 0;
  cout << "Enter a number of candies:";
  int number;
  cin >> number;

  while (number >= 1000) {
    cout << "Please enter an integer number between 0 and 999.\n";
    cin >> number;
  }

  for (  ; times <= 10; times++, number--) {
    cout << "nomnom I have" << number << "candies left.\n";
   }

   return;
}

So I have to write for ( int times = 1; number < 1000 && times <=10; number--) ? — Théo, Dec 06 '19 at 00:07

score 0 · Answer 3 · edited Dec 06 '19 at 06:27

0

You're pretty close! There was just a slight issue with the for loop syntax:

The first part of the for loop is actually the initializer, the middle bit is the conditional, and the last bit is the iterator, it's a bit different than the while loop.

Here is what you probably meant to do:

  for (times = 0; times < 9; number--, times++) {
    cout << "nomnom I have" << number - 1 << "candies left.\n";    
  }

edited Dec 06 '19 at 06:27

Gaben

345
1
12

answered Dec 05 '19 at 23:59

Tor

1

I tried doing that, but it gives me an error message. – Théo Dec 07 '19 at 01:44

C++ while loops and for loops not working

3 Answers3