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Because the while loop checks the condition/expression before the block is executed, the control structure is often also known as a pre-test loop. Compare this with the do while loop, which tests the condition/expression after the loop has executed. For example, in the languages C, Java, C#, [2] Objective-C, and C++, (which use the same syntax ...
In the C programming language, Duff's device is a way of manually implementing loop unrolling by interleaving two syntactic constructs of C: the do-while loop and a switch statement. Its discovery is credited to Tom Duff in November 1983, when Duff was working for Lucasfilm and used it to speed up a real-time animation program.
LOOP is a simple register language that precisely captures the primitive recursive functions. [1] The language is derived from the counter-machine model. Like the counter machines the LOOP language comprises a set of one or more unbounded registers, each of which can hold a single non-negative integer. A few arithmetic instructions (like 'CleaR ...
A conditional loop has the potential to become an infinite loop when nothing in the loop's body can affect the outcome of the loop's conditional statement. However, infinite loops can sometimes be used purposely, often with an exit from the loop built into the loop implementation for every computer language , but many share the same basic ...
The Eiffel programming language provides native support for loop invariants. [6] A loop invariant is expressed with the same syntax used for a class invariant. In the sample below, the loop invariant expression x <= 10 must be true following the loop initialization, and after each execution of the loop body; this is checked at runtime.
This control structure can be known as a post-test loop. This means the do-while loop is an exit-condition loop. However a while loop will test the condition before the code within the block is executed. This means that the code is always executed first and then the expression or test condition is evaluated.
Here is an example, in C-like pseudocode, of an integer variant computed from some upper bound on the number of iterations remaining in a while loop. However, C allows side effects in the evaluation of expressions, which is unacceptable from the point of view of formally verifying a computer program.
The test for i < len is still present, but it has been moved outside the loop, which now contains only a single test (for the value), and is guaranteed to terminate due to the sentinel value. There is a single check on termination if the sentinel value has been hit, which replaces a test for each iteration.