Icon+Unicon/Intro: Difference between revisions

Suspend is semantically similar to 'return' with the exception that it sets up the possibility of producing additional results if needed. Rather than terminating the procedure as return does, suspend returns a result while leaving the procedure in suspension in the event additional results are needed. A suspended procedure will resume at the next point in the code. This capability is built directly into the run time rather than being an artificially constructed behaviour provided by Python or C#'s use of the 'yield' keyword. Every and all expressions may suspend or be involved in a suspending expression without any effort. Behaviorally this is closer to Prolog which also supports backtracking as a core part of the language. If the ''expr'' is capable of yielding more than one result, then suspend (if driven) will progressively yield all of those values. If the expression fails, execution continues within the procedure until the next suspend, return, or fail.