CODEWITHSUNDEEP
c++loopsfor-loopwhile-loop

Reputation:

How do you Make A Repeat-Until Loop in C++?

How do you Make A Repeat-Until Loop in C++? As opposed to a standard While or For loop. I need to check the condition at the end of each iteration, rather than at the beginning.

Upvotes: 33

Views: 204807

Answers (7)

C Console
C Console

Reputation: 11

This can also work

    int repeat;
    repeat = 0;
    //to repeat once
    do  {
       ....
       repeat + 1;
    } while(repeat < 1);

This is of course assuming you want to only repeat once, so you can change the value of repeat, not the amount of it's increase from the variable amount from the while(); condition. This code works for C++ 17, but I am not sure for other versions.

Upvotes: 1

Gilles Page
Gilles Page

Reputation: 19

Repeat is supposed to be a simple loop n times loop... a conditionless version of a loop.

#define repeat(n) for (int i = 0; i < n; i++) 

repeat(10) {
    //do stuff
}

you can also also add an extra barce to isolate the i variable even more

#define repeat(n) { for (int i = 0; i < n; i++) 
#define endrepeat }

repeat(10) {
    //do stuff
} endrepeat;

[edit] Someone posted a concern about passing a something other than a value, such as an expression. just change to loop to run backwards, causing the expression to be evaluated only once

#define repeat(n) { for (int i = (n); i > 0; --i)

Upvotes: 0

rOhAn703
rOhAn703

Reputation: 41

Just use:

do
{
  //enter code here
} while ( !condition );

So what this does is, it moves your 'check for condition' part to the end, since the while is at the end. So it only checks the condition after running the code, just like how you want it

Upvotes: 4

weiwangchao
weiwangchao

Reputation: 117

You could use macros to simulate the repeat-until syntax.

#define repeat do
#define until(exp) while(!(exp))

Upvotes: 10

Kehlin Swain
Kehlin Swain

Reputation: 481

For an example if you want to have a loop that stopped when it has counted all of the people in a group. We will consider the value X to be equal to the number of the people in the group, and the counter will be used to count all of the people in the group. To write the

while(!condition)

the code will be:

int x = people;

int counter = 0;

while(x != counter)

{

counter++;

}

return 0;

Upvotes: 2

Adrien
Adrien

Reputation: 3195

do
{
  //  whatever
} while ( !condition );

Upvotes: 55

Zifre
Zifre

Reputation: 26998

When you want to check the condition at the beginning of the loop, simply negate the condition on a standard while loop:

while(!cond) { ... }

If you need it at the end, use a do ... while loop and negate the condition:

do { ... } while(!cond);

Upvotes: 10

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