Go to statement considered harmful. Author: Edsger W. Dijkstra, Technological University, Eindhoven, The Netherlands View colleagues of Edsger W. Dijkstra . “GOTO considered harmful” needs to be read in its historical context, where structured programming (for Thanks for posting Dijkstra answer. One of the comments did mention Dijkstra’s article Go to Statements Considered Harmful, but aside from that mention, there was much.

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The comments associated with that post that post mostly repeated the pattern of the Usenet discussion: How do we deal with goto statements when we are trying to understand what a program does?

This type of use of goto statements is generally accepted as a “correct” use of goto. Coding Tools Building Node. These constructs allow for the loop-and-a-half situations that sometimes arise which is discussed further below. Here, finally, we get to the crux of Dijkstra’s argument concerning the lowly goto statement. Dobb’s Journal is devoted to mobile programming. The abuse of GOTO is, thankfully, a long forgotten memory in today’s modern programming languages.

I’d Consider That Harmful, Too

That’s a very common C idiom. Any form of system programming harkful c will probably have lots of goto’s. GalacticDomin8r on Feb 8, Some examples of inadequate flow control constructs are discussed in more detail below.

Many functional programming languages, such as LISP, Scheme, and Prolog, do not provide traditional structured flow control constructs beyond if-then-else or only provide very simple forms of them. Some languages, such as Java, provide a finally clause as part of the try-catch statement to provide a way to specify actions that must be taken regardless of whether or not an exception occurs. Here Dijkstra acknowledges the influences that led him to his observation about the dangers of goto.

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Since the s, several advances in harrmful theory have occurred. More primitive languages such as FORTRAN, COBOL, C, Pascal, and the like may provide some kinds of primitive exception handling mechanisms, but their use does not guarantee that the execution state is cleanly preserved or that allocated resources will be properly released. The discipline of programming has progressed through several phases, with each new advance being touted as the next “better” way of programming.

If you want to maximize the effectiveness of your criticisms, however, you’ll leave “considered harmful” out of your writing. Goto can be very useful when used carefully, most often for a “cleanup” block, as used in the example above. Other variants of the for-loop allow more than one loop counter or loop index to be specified. Optimizers have also gotten better over the years–it would be fairly easy to transform the idiomatic find-loop pattern based on flags to the one that uses the goto.

Dijkstra mentions abortion clausesor what is now commonly known as exception handlershinting that these kinds of things are really fancy gotos underneath, but that they can be defined so that they behave well dojkstra the confines of a structured language, i.

Apocryphon on Feb 8, For languages that lack robust exception handling mechanisms, gotos may be the only practical substitute. Programming Language Newsgroups groups. This second construct is the most obvious replacement for the unstructured test-and-goto construct:. On the surface, this loop is no harder to analyze than the earlier cpnsidered all, it behaves in the same way.

Dijkstra reminds us that it was originally proposed as a superior alternative to the clumsy use of multiple if s, goto s, and labels. And so now we have — yes — return, and also break, exceptions, etc.

I’m rather surprised that the idea of a multi-level break, which has been proposed for more than one PL, has never really caught on. PeCaN on Feb 8, Roboprog on Feb 8, Thesis, antithesis, synthesis. One of the comments did mention Dijkstra’s article Go to Statements Considered Harmfulbut aside from that mention, there was much opinion and little fact.


Imagine the authors horror had he witnessed the use of properties in modern object oriented languages! In order to speed up its publication, the paper was converted into a “Letter to the Editor”.

Go To Statement Considered Harmful

Both cases complicate the consudered in which the counters in the loop iteration stack are modified. Dijkstra introduces fijkstra topic of his letter, which is that he has noticed that goto statements are mostly detrimental to the programs in which they appear.

Since then, programming technology has evolved through the stages of structured programming, top-down programming, object-oriented programming, component programming, aspect programming, and beyond. Also some algos express them self best using goto’s.

It is more difficult in some languages especially some older languages to write multiple if-then sequences, so the construct ends up looking like the following code, which is functionally equivalent but harder to read:. Most Popular Stories Blogs. With the inclusion of the repetition clauses textual indices are no longer sufficient dujkstra describe the dynamic progress of the process.

Dijkstra points to a number of bugs in the second and third versions of the program i. However, to some extent Dijkstra’s principle has not been fully realized when we observe the complexity that must be dealt with by real-world programming tasks, such as multitasking, multithreading, interrupt handling, volatile hardware registers, virtual memory paging, device latency, real-time event handling, and so forth, just to name a few.