D Programming - Loops

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There may be a situation, when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

Programming languages provide various control structures that allow more complicated execution paths.

A loop statement executes a statement or group of statements multiple times. The following general form of a loop statement in mostly used in the programming languages −

Loop Architecture

D programming language provides the following types of loop to handle looping requirements. Click the following links to check their detail.

Sr.No. Loop Type & Description
1 while loop

It repeats a statement or group of statements while a given condition is true. It tests the condition before executing the loop body.
2 for loop

It executes a sequence of statements multiple times and abbreviates the code that manages the loop variable.
3 do...while loop

Like a while statement, except that it tests the condition at the end of the loop body.
4 nested loops

You can use one or more loop inside any another while, for, or do..while loop.

Loop Control Statements

Loop control statements change execution from its normal sequence. When execution leaves a scope, all automatic objects that were created in that scope are destroyed.

D supports the following control statements −

Sr.No. Control Statement & Description
1 break statement

Terminates the loop or switch statement and transfers execution to the statement immediately following the loop or switch.
2 continue statement

Causes the loop to skip the remainder of its body and immediately retest its condition prior to reiterating.

The Infinite Loop

A loop becomes infinite loop if a condition never becomes false. The for loop is traditionally used for this purpose. Since none of the three expressions that form the for loop are required, you can make an endless loop by leaving the conditional expression empty.

import std.stdio;

int main () {

   for( ; ; ) {
      writefln("This loop will run forever.");
   }
   return 0;
}

When the conditional expression is absent, it is assumed to be true. You may have an initialization and increment expression, but D programmers more commonly use the for(;;) construct to signify an infinite loop.

NOTE − You can terminate an infinite loop by pressing Ctrl + C keys.

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