Structured programming
These issues were addressed during the late 1960s and early 1970s, with major contributions by Dijkstra, Robert W. Floyd, Tony Hoare, Ole-Johan Dahl, and David Gries.Neither the proof by Böhm and Jacopini nor our repeated successes at writing structured code brought them around one day sooner than they were ready to convince themselves.[8] In his 1974 paper, "Structured Programming with Goto Statements",[9] he gave examples where he believed that a direct jump leads to clearer and more efficient code without sacrificing provability.The project was a great engineering success, and managers at other companies cited it in support of adopting structured programming, although Dijkstra criticized the ways that Mills's interpretation differed from the published work.In structured programming, these can be replicated by adding additional branches or tests, but for returns from nested code this can add significant complexity.Kent Beck, Martin Fowler and co-authors have argued in their refactoring books that nested conditionals may be harder to understand than a certain type of flatter structure using multiple exits predicated by guard clauses.[15] In contrast to the above, Bertrand Meyer wrote in his 2009 textbook that instructions like break and continue "are just the old goto in sheep's clothing" and strongly advised against their use.Bonang proposes that all single-exit conforming C++ should be written along the lines of: Peter Ritchie also notes that, in principle, even a single throw right before the return in a function constitutes a violation of the single-exit principle, but argues that Dijkstra's rules were written in a time before exception handling became a paradigm in programming languages, so he proposes to allow any number of throw points in addition to a single return point.[20] Citing multiple prior studies by others (1999–2004) and their own results, Westley Weimer and George Necula wrote that a significant problem with exceptions is that they "create hidden control-flow paths that are difficult for programmers to reason about".[21] The necessity to limit code to single-exit points appears in some contemporary programming environments focused on parallel computing, such as OpenMP.From a code execution point of view, yielding from a coroutine is closer to structured programming than returning from a subroutine, as the subprogram has not actually terminated, and will continue when called again – it is not an early exit.However, coroutines mean that multiple subprograms have execution state – rather than a single call stack of subroutines – and thus introduce a different form of complexity.[citation needed] However, it is possible to structure these systems by making each state-change a separate subprogram and using a variable to indicate the active state (see trampoline).
programming paradigmcomputer programcontrol flowif/then/elseblock structuressubroutinesALGOL 58ALGOL 60structured program theoremGo To Statement Considered HarmfulEdsger W. Dijkstraexception handlingcontrol structureskeywordsif..then..else..endifrepeatdo..untilthree basic patternsNS diagramsflow chartsBlocksALGOL 68PascalwhitespacePythonprocedural programming languageunstructured programmingcomputable functioninstruction cyclecentral processing unitTuring machineDijkstraRobert W. FloydTony HoareOle-Johan DahlDavid GriesP. J. Plaugerearly adopterDonald Knuthflow chartcompilersgraph theoryreducible flow graphsHarlan MillsThe New York TimesFORTRANreturn statementReturn earlymemory leaksresource leaksresource managementResource Acquisition Is InitializationKent BeckMartin Fowlerrefactoringguard clausesHerb SutterAndrei AlexandrescuDavid Wattsequencerspaghetti codeBertrand MeyerException handling (programming)Ariane 501 disastercargo cultdefault behaviorGeorge Neculaparallel computingOpenMPCoroutinegeneratorstreamsparserscommunications protocolsstatestrampolineDRAKONMinimal evaluationNassi–Shneiderman diagramStructure chartStructured concurrencySwitch statementPlauger, P. J.University of Wisconsin–MadisonEdsger DijkstraBöhm, CorradoCommunications of the ACMCiteSeerXDijkstra, Edsger W.Michael A. JacksonO.-J. DahlE. W. DijkstraC. A. R. Hoare8 Queens problemProgramming paradigmsComparison by languageImperativeJackson structuresBlock-structuredModularNon-structuredProceduralProgramming in the large and in the smallDesign by contractInvariant-basedNested functionObject-orientedcomparisonClass-basedPrototype-basedObject-basedImmutable objectPersistentUniform Function Call SyntaxDeclarativeFunctionalRecursiveAnonymous functionPartial applicationHigher-orderPurely functionalStrictDependent typesFunctional logicPoint-free styleExpression-oriented