Meta tags:
Headings (most frequently used words):
loop, control, branch, condition, and, handling, early, exit, flow, contents, structure, see, also, references, external, links, sequences, labels, blocks, functions, branches, loops, non, local, jump, conditional, multiway, numeric, controlled, enumeration, infinite, half, problem, unstructured, variants, invariants, sublanguage, system, cross, reference, table, exception, continuation, generator, coroutine, comefrom, event, based, from, nested, middle, test, multi, level, breaks,
Text of the page (most frequently used words):
the (321), yes (139), loop (134), and (103), control (84), for (79), statement (53), that (53), #nested (52), code (51), with (50), example (50), deep (44), from (43), edit (43), programming (41), flow (36), this (36), languages (34), can (34), not (33), language (31), while (31), are (29), condition (28), when (26), then (25), which (25), some (23), articles (22), exit (22), test (22), exception (21), point (21), case (21), iteration (20), retrieved (20), statements (20), level (20), program (19), loops (19), break (19), such (19), goto (18), structure (18), used (18), jump (18), one (18), end (18), may (17), computer (17), execution (17), fortran (16), following (16), xxx (16), early (16), comefrom (16), breaks (16), was (15), has (15), infinite (15), label (15), jumps (15), constructs (14), many (14), value (14), other (14), else (14), python (13), structured (13), also (13), executed (13), but (13), function (13), conditional (13), command (13), using (12), common (12), after (12), line (12), table (11), use (11), foreach (11), first (11), called (11), ruby (10), pdf (10), archived (10), 1974 (10), generator (10), handling (10), continuation (10), stream (10), only (10), multi (10), body (10), perl (9), lisp (9), java (9), where (9), knuth (9), general (9), item (9), similar (9), action (9), construct (9), based (9), there (9), instead (9), return (9), try (9), most (9), numeric (9), done (9), part (9), branch (9), non (8), pascal (8), ada (8), original (8), all (8), does (8), half (8), 2020 (8), print (8), any (8), than (8), uses (8), syntax (8), type (8), variants (8), integer (8), each (8), basic (8), repeat (8), wikipedia (7), page (7), php (7), org (7), article (7), via (7), section (7), what (7), bash (7), reference (7), simple (7), data (7), get (7), until (7), both (7), collection (7), middle (7), next (7), main (7), last (6), less (6), acm (6), science (6), machine (6), commands (6), construction (6), list (6), problem (6), conditions (6), found (6), out (6), provides (6), even (6), specified (6), reaches (6), requires (6), since (6), often (6), coroutine (6), have (6), been (6), functions (6), coroutines (6), values (6), like (6), state (6), times (6), block (6), including (6), clause (6), number (6), support (6), call (6), cases (6), supported (6), although (6), include (6), start (6), switch (6), terms (5), links (5), considered (5), 2019 (5), 978 (5), 2016 (5), how (5), between (5), eiffel (5), stack (5), operator (5), lists (5), dijkstra (5), std (5), exits (5), software (5), event (5), proposed (5), implemented (5), more (5), depending (5), processing (5), logic (5), must (5), excerpt (5), generators (5), special (5), sequence (5), however (5), object (5), catch (5), dosomething (5), unstructured (5), supports (5), these (5), true (5), provide (5), invariants (5), form (5), usually (5), displaystyle (5), another (5), keyword (5), actiononnomatch (5), actiononyandz (5), actiononx (5), actionona (5), somechar (5), printf (5), toggle (4), contents (4), search (4), commons (4), haskell (4), short (4), manual (4), harmful (4), top (4), doi (4), 2004 (4), compiler (4), isbn (4), overflow (4), error (4), looping (4), kosaraju (4), 2024 (4), redo (4), process (4), see (4), exitwhen (4), exceptions (4), variant (4), occurs (4), before (4), local (4), term (4), they (4), continuations (4), current (4), step (4), implements (4), being (4), create (4), file (4), whether (4), set (4), handler (4), someexception (4), standard (4), possible (4), iterate (4), over (4), added (4), labels (4), increment (4), builtin (4), per (4), arrays (4), begin (4), sublanguage (4), negative (4), shell (4), either (4), multilevel (4), continue (4), various (4), second (4), repeated (4), controlled (4), expressions (4), string (4), default (4), instruction (4), imperative (4), hide (4), move (4), sidebar (4), topic (3), view (3), about (3), additional (3), you (3), wikimedia (3), smalltalk (3), wikidata (3), wayback (3), index (3), related (3), external (3), 2014 (3), 1145 (3), design (3), diagram (3), history (3), donald (3), collections (3), net (3), 2010 (3), com (3), macro (3), 2025 (3), watt (3), 1973 (3), system (3), false (3), open (3), information (3), named (3), lang (3), perldoc (3), way (3), iterations (3), endless (3), new (3), algorithm (3), complexity (3), modeling (3), missing (3), target (3), endexit (3), searching (3), occur (3), here (3), instructions (3), written (3), intercal (3), others (3), same (3), order (3), depends (3), transfers (3), will (3), entire (3), specifies (3), later (3), components (3), class (3), always (3), rather (3), returns (3), containing (3), once (3), allows (3), immediately (3), processstuff (3), filestream (3), propagates (3), effect (3), caught (3), typical (3), integers (3), retry (3), range (3), through (3), because (3), visual (3), native (3), invariant (3), during (3), expression (3), omitted (3), reversing (3), read (3), char (3), sequencers (3), sequencer (3), commonly (3), depth (3), without (3), labeled (3), contains (3), style (3), solution (3), least (3), performed (3), duplicated (3), inside (3), unless (3), iterates (3), functional (3), multiway (3), matching (3), branches (3), foo (3), void (3), sequences (3), success (3), sequential (3), progresses (3), tools (3), add (2), legal (2), contact (2), privacy (2), policy (2), organization (2), september (2), hidden (2), categories (2), javascript (2), algol (2), link (2), template (2), description (2), 2009 (2), linguistic (2), wikibook (2), zahn (2), presented (2), natural (2), william (2), july (2), 2018 (2), datamation (2), don (2), know (2), come (2), lawrence (2), 1963 (2), s2cid (2), conway (2), melvin (2), vol (2), 2023 (2), anthony (2), nature (2), encyclopedia (2), scheme (2), difference (2), iterator (2), boost (2), for_each (2), comma (2), gnu (2), implementation (2), make (2), throw (2), dahl (2), press (2), 1972 (2), david (2), rao (2), analysis (2), programs (2), theory (2), computing (2), cited (2), theorem (2), notes (2), 540 (2), pep (2), 3136 (2), docs (2), control_expressions (2), documentation (2), them (2), personal (2), 278 (2), edsger (2), www (2), examples (2), endgame (2), reading (2), attack (2), properties (2), references (2), source (2), represents (2), tool (2), representation (2), two (2), dimensional (2), purpose (2), events (2), within (2), their (2), indicated (2), very (2), clear (2), situation (2), eventa (2), eventb (2), eventc (2), version (2), seen (2), joke (2), along (2), were (2), assembly (2), multiple (2), otherwise (2), needed (2), processor (2), resulting (2), argument (2), opposite (2), iterators (2), cooperative (2), known (2), back (2), caller (2), array (2), returning (2), time (2), would (2), ability (2), possibly (2), given (2), useful (2), runtime (2), filemode (2), logfile (2), txt (2), pattern (2), null (2), finally (2), divide (2), zero (2), result (2), mynumber (2), keywords (2), applescript (2), println (2), types (2), propagated (2), exceptional (2), starts (2), raised (2), proceeds (2), inner (2), handles (2), normal (2), handlers (2), flows (2), aspects (2), had (2), especially (2), subscriptrange (2), programmers (2), avoid (2), define (2), interest (2), check (2), those (2), dynamic (2), notable (2), odin (2), concept (2), procedures (2), specification (2), stl (2), functionality (2), containers (2), accomplished (2), counting (2), iterating (2), incrementing (2), apl (2), powershell (2), rust (2), correctness (2), cross (2), contain (2), implies (2), terminates (2), constructions (2), allow (2), idiomatic (2), script (2), single (2), traditional (2), bottom (2), polarity (2), adding (2), xxx2 (2), xxx1 (2), notion (2), defined (2), cannot (2), variables (2), furthermore (2), hierarchy (2), exists (2), together (2), currently (2), usual (2), alternative (2), implement (2), prime (2), beginning (2), results (2), explicitly (2), skipped (2), checking (2), sometimes (2), solutions (2), scala (2), asynchronous (2), somecollection (2), coll (2), somearray (2), enumeration (2), three (2), pre (2), family (2), variations (2), hardware (2), might (2), rounding (2), relatively (2), larger (2), recursive (2), gets (2), select (2), match (2), shows (2), echo (2), puts (2), writeln (2), messages (2), arithmetic (2), high (2), closely (2), follows (2), describes (2), blocks (2), identifies (2), position (2), confused (2), alters (2), appearance (2), upload (2), changes (2), subsection (2), log (2), account (2), donate (2), menu (2), mobile, cookie, statistics, developers, conduct, safety, contacts, disclaimers, text, available, under, apply, site, agree, registered, trademark, profit, foundation, inc, creative, attribution, sharealike, license, rendered, parsoid, edited, 2026, utc, matlab, octave, sharp, category, excerpts, webarchive, different, recursion, comparisons, https, title, control_flow, oldid, 1374573496, ibm, 704, contribution, media, symposium, paris, down, modell, howard, slater, april, 1978, 953411, 953418, sigplan, notices, innovation, lives, expectations, clarke, 408, 2022, digital, library, 10559786, 0001, 0782, issn, 366663, 366704, 396, communications, separable, transition, 1997, art, 3rd, addison, wesley, bibliography, 229, 201, 89683, fundamental, algorithms, ervin, tall, snarky, canadian, heck, async, await, work, ralston, 2000, pub, group, 2013, 56159, 248, kiselyov, oleg, january, ways, traverse, sandbox, sourceforge, chapter, sgi, meyer, bertrand, 1991, prentice, hall, 131, 129, exchange, could, prone, hoare, academic, findlay, john, wiley, sons, 221, 470, 85320, 215, concepts, proc, fifth, annual, syrup, 240, 252, sciences, december, kozen, dexter, 2008, böhm, jacopini, propositionally, lecture, 5133, 192, 70593, 1007, 70594, 9_11, 177, mathematics, guido, van, rossum, 3000, announcing, technology, comp, faq, question, 20b, advanced, scripting, guide, solve, 279, communication, wikiwikiweb, messy, dictionary, definition, dean, jenna, startup, w3schools, geeksforgeeks, roberts, 1995, sigcse, bulletin, 268, 272, reopening, debate, 301, 207630080, 356635, 356640, 261, surveys, release, prnewswire, present, black, hat, usa, november, 2015, dark, adobe, flash, bug, discovery, leads, mitigation, method, kuznetsov, volodymyr, nebelwelt, differences, cfi, cps, cpi, payer, mathias, poor, spaghetti, workflow, flowchart, mapping, drakon, measure, structural, cyclomatic, graphical, graph, business, technique, involves, particular, conceptually, specify, occurrence, name, relevant, carried, passes, just, separation, determining, applies, taken, actiona, actionb, actionc, discussed, modified, initially, cmfrm, elaborated, upon, clark, response, letter, eventually, obscure, computed, proposals, assigned, dont, complement, existing, esoteric, semantics, varies, invalid, deterministic, induce, citation, threaded, concurrent, parallel, major, global, interpreter, scan, points, tends, difficult, understand, indication, near, fact, study, causes, intended, serious, identified, continues, coined, 1958, applied, published, explanation, appeared, described, whose, pause, suspended, resumed, generalizing, well, suited, implementing, familiar, pipes, tasks, multitasking, subroutines, expressive, semicoroutines, weaker, yield, passing, specifying, comparison, behaviour, generates, building, started, few, behaves, looks, memory, yields, parameters, routine, computation, perspective, running, derived, refer, give, save, computational, created, accessed, encoding, mechanisms, environment, reifies, abstract, ensure, cleanup, released, close, rest, ensures, closed, display, dialog, partial, introduce, incorporates, placeholders, extract, shown, donextthing, unknown, const, demonstrates, matches, message, printed, modern, natively, generally, thrown, reverts, outward, outermost, scope, progressively, outer, normally, popping, handled, automatically, unfortunately, implementations, substantial, overhead, space, tried, decide, should, resume, zerodivide, endfile, intercepted, own, earliest, compilers, independence, included, 2003, numerical, issues, calls, module, ieee_exceptions, quotient, accumulator, favoring, styles, offer, cause, follow, predeclared, shortcuts, predates, generic, achieved, require, transfinite, why, jml, behavioral, interface, reserved, word, effected, across, interval, introduced, element, constructed, unary, users, simulated, instance, objects, gotos, specifically, init, count, dedicated, zig, swift, rebol, qb64, ocaml, maybe, kotlin, cobol, facilities, dialects, extensive, describing, conversional, interlisp, assertion, remain, correctly, satisfied, monitor, specific, successive, practical, initial, decrease, never, become, correct, guarantee, terminate, express, strlen, read_string, marginal, primarily, modify, statement_b, statement_a, statement_2, statement_1, shoehorning, into, status, separated, newlines, above, consequent, works, accepts, formally, bourne, forth, widely, thought, further, omitting, individual, replace, several, equivalent, keeping, unlike, functioning, atendoffile, write, his, textbook, tennent, explain, similarity, textually, enclosing, procedure, encompasses, carry, whereas, contemporary, escape, gives, rise, today, refined, proving, long, arbitrary, allowed, proved, strict, every, rewritten, introducing, theoretical, breaking, circles, levels, alternatives, variable, tested, broken, placing, termination, neither, nor, inclusion, feature, rejected, basis, worth, rare, legitimate, c29, did, numbers, isprime, set_of_numbers, exited, linked, occurred, stop, restarts, restart, cycle, skip, completion, criteria, continuing, subtlety, rewriting, recognized, 1967, wirth, suggesting, solving, 1990s, taught, dubbed, now, preparing, structures, arises, reasons, eliminate, minimize, duplication, having, duplicating, wrapping, determine, halting, endlessly, intervention, turning, off, power, pulling, plug, intentional, generalise, comprehensions, forall, alias, mystringcollection, tcl, mycollection, raku, eachelement, enumerate, items, int, evaluated, place, initialize, third, elsewhere, post, completely, reliably, floating, represented, imprecisely, due, constraints, factors, addition, accumulated, errors, mean, differ, quite, significantly, expected, yet, ends, smaller, processes, expressed, syntactic, tail, iterative, frequently, previous, met, hand, outside, infinitely, indefinite, definite, esac, provision, optimizations, limited, constant, extend, right, decode, sql, glob, lookup, tables, plusp, princ, conditionals, iffalse, iftrue, supplements, ternary, tests, positive, deemed, obsolete, deleted, restricted, mimics, boolean, provided, upper, lower, words, scientists, unconditionally, controlling, moves, bar, completes, calling, completing, printing, devised, organized, still, workin, organizing, curly, braces, delimit, bool, alphanumeric, appearing, followed, colon, defines, identifier, let, limit, inherent, none, typically, required, marking, lines, rules, limits, sequencing, selection, redirect, variety, techniques, shadow, stacks, pointer, verification, defend, against, attacks, vtable, buffer, protection, canaries, integrity, transfer, interrupted, signal, interrupt, unconditional, approach, conditionally, enables, branching, predication, counter, central, unit, encodes, focused, desired, prescribing, operations, though, declarative, paradigms, contexts, sequentially, located, executing, except, classified, context, its, redirected, free, wikibooks, projects, printable, download, export, legacy, parser, shortened, url, cite, permanent, actions, english, talk, tiếng, việt, اردو, українська, ไทย, தமிழ், svenska, српски, srpski, srpskohrvatski, српскохрватски, русский, português, polski, norsk, bokmål, nederlands, bahasa, melayu, 한국어, қазақша, 日本語, italiano, íslenska, hrvatski, עברית, français, فارسی, euskara, español, esperanto, deutsch, čeština, català, azərbaycanca, العربية, pages, recent, community, portal, learn, help, contribute, random, navigation, content,
Text of the page (random words):
is not widely supported with most languages instead using if break for conditional early exit this is supported by some languages such as forth where the syntax is begin while repeat 31 and the shell script languages bourne shell sh and bash where the syntax is while do done or until do done as 32 33 while statement 1 statement 2 condition do statement a statement b done the shell syntax works because the while or until loop accepts a list of commands as a condition 34 formally while test commands do consequent commands done the value exit status of the list of test commands is the value of the last command and these can be separated by newlines resulting in the idiomatic form above similar constructions are possible in c and c with the comma operator and other languages with similar constructs which allow shoehorning a list of statements into the while condition while statement_1 statement_2 condition statement_a statement_b while legal this is marginal and it is primarily used if at all only for short modify then test cases as in 35 while read_string s strlen s 0 loop variants and invariants edit loop variants and loop invariants are used to express correctness of loops 36 in practical terms a loop variant is an integer expression which has an initial non negative value the variant s value must decrease during each loop iteration but must never become negative during the correct execution of the loop loop variants are used to guarantee that loops will terminate a loop invariant is an assertion which must be true before the first loop iteration and remain true after each iteration this implies that when a loop terminates correctly both the exit condition and the loop invariant are satisfied loop invariants are used to monitor specific properties of a loop during successive iterations some programming languages such as eiffel contain native support for loop variants and invariants in other cases support is an add on such as the java modeling language s specification for loop statements in java loop sublanguage edit some lisp dialects provide an extensive sublanguage for describing loops an early example can be found in conversional lisp of interlisp common lisp 37 provides a loop macro which implements such a sublanguage loop system cross reference table edit programming language conditional loop early exit loop continuation redo retry correctness facilities begin middle end numeric collection general infinite 1 variant invariant ada yes yes yes yes arrays no yes deep nested no apl yes no yes yes yes yes yes deep nested 3 yes no no c yes no yes no 2 no yes no deep nested 3 deep nested 3 no no no no c yes no yes no 2 yes 9 yes no deep nested 3 deep nested 3 no no no no c yes no yes no 2 yes yes no deep nested 3 deep nested 3 no no no no cobol yes no yes yes no yes no deep nested 15 deep nested 14 no common lisp yes yes yes yes builtin only 16 yes yes deep nested no d yes no yes yes yes yes yes 14 deep nested deep nested no eiffel yes no no yes 10 yes yes no one level 10 no no no 11 integer only 13 yes f yes no no yes yes no no no 6 no no fortran 77 yes no no yes no no no one level yes no no fortran 90 yes no no yes no no yes deep nested deep nested no no fortran 95 and later yes no no yes arrays no yes deep nested deep nested no no go yes no no yes builtin only yes yes deep nested deep nested no haskell no no no no yes no yes no 6 no no java yes no yes no 2 yes yes no deep nested deep nested no non native 12 non native 12 javascript yes no yes no 2 yes yes no deep nested deep nested no no no kotlin yes no yes maybe yes no no deep nested deep nested no no no no natural yes yes yes yes no yes yes yes yes yes no ocaml yes no no yes arrays lists no no no 6 no no odin no 17 no no no 5 builtin only yes no 17 deep nested deep nested php yes no yes no 2 5 yes 4 yes no deep nested deep nested no no no no perl yes no yes no 2 5 yes yes no deep nested deep nested yes python yes no no no 5 yes no no deep nested 6 deep nested 6 no no no no qb64 yes no yes yes no yes yes one level per type of loop one level per type of loop no no no no rebol no 7 yes yes yes yes no 8 yes one level 6 no no ruby yes no yes yes yes no yes deep nested 6 deep nested 6 yes yes rust yes no no no 5 yes no yes deep nested deep nested no no no no standard ml yes no no no arrays lists no no no 6 no no swift yes no yes no yes yes no deep nested deep nested no no no no visual basic net yes no yes yes yes no yes one level per type of loop one level per type of loop no no no no powershell yes no yes no 2 yes yes no yes yes no no no no zig yes no no yes builtin only no no deep nested deep nested no no no no a while true does not count as an infinite loop for this purpose because it is not a dedicated language structure a b c d e f g h c s for init test increment loop is a general loop construct not specifically a counting one although it is often used for that a b c deep breaks may be accomplished in apl c c and c through the use of labels and gotos a iteration over objects was added in php 5 a b c d e f a counting loop can be simulated by iterating over an incrementing list or generator for instance python s range a b c d e deep breaks may be accomplished through the use of exception handling a there is no special construct since the while function can be used for this a there is no special construct but users can define general loop functions a the c 11 standard introduced the range based for in the stl there is a std for_each template function which can iterate on stl containers and call a unary function for each element 38 the functionality also can be constructed as macro on these containers 39 a numeric looping is effected by iteration across an integer interval early exit by including an additional condition for exit a eiffel supports a reserved word retry however it is used in exception handling not loop control a requires java modeling language jml behavioral interface specification language a requires loop variants to be integers transfinite variants are not supported eiffel why loop variants are integers a d supports infinite collections and the ability to iterate over those collections this does not require any special construct a deep breaks can be achieved using go to and procedures a common lisp predates the concept of generic collection type a b odin s general for loop supports syntax shortcuts for conditional loop and infinite loop non local edit many programming languages especially those favoring more dynamic styles of programming offer constructs for non local control flow which cause execution to jump from the current execution point to a predeclared point notable examples follow condition handling edit the earliest fortran compilers supported statements for handling exceptional conditions including if accumulator overflow if quotient overflow and if divide check in the interest of machine independence they were not included in fortran iv and the fortran 66 standard however since fortran 2003 it is possible to test for numerical issues via calls to functions in the ieee_exceptions module pl i has some 22 standard conditions e g zerodivide subscriptrange endfile which can be raised and which can be intercepted by on condition action programmers can also define and use their own named conditions like the unstructured if only one statement can be specified so in many cases a goto is needed to decide where flow of control should resume unfortunately some implementations had a substantial overhead in both space and time especially subscriptrange so many programmers tried to avoid using conditions a typical example of syntax on condition goto label exception handling edit many modern languages natively support exception handling generally exceptional control flow starts with an exception object being thrown a k a raised control then proceeds to the inner most exception handler for the call stack if the handler handles the exception then flow control reverts to normal otherwise control proceeds outward to containing handlers until one handles the exception or the program reaches the outermost scope and exits as control flows to progressively outer handlers aspects that would normally occur such as popping the call stack are handled automatically the following c code demonstrates structured exception handling if an exception propagates from the execution of dosomething and the exception object type matches one of the types specified in a catch clause then that clause is executed for example if an exception of type someexception is propagated by dosomething then control jumps from line 2 to 4 and the message caught someexception is printed and then control jumps to after the try statement line 8 if an exception of any other type is propagated then control jumps from line 2 to 6 if no exception then control jumps from 2 to 8 try dosomething catch const someexception e std println caught someexception e what catch std println unknown error donextthing many languages use the c keywords throw try and catch but some languages use other keywords for example ada uses exception to introduce an exception handler and when instead of catch applescript incorporates placeholders in the syntax to extract information about the exception as shown in the following applescript code try set mynumber to mynumber 0 on error e number n from f to t partial result pr if e can t divide by zero then display dialog you must not do that end try in many languages including object pascal d java c and python a finally clause at the end of a try statement is executed at the end of the try statement whether an exception propagates from the rest of the try or not the following c code ensures that the stream stream is closed filestream stream null try stream new filestream logfile txt filemode create return processstuff stream finally if stream null stream close since this pattern is common c provides the using statement to ensure cleanup in the following code even if processstuff propagates an exception the stream object is released python s with statement and ruby s block argument to file open are used to similar effect using filestream stream new logfile txt filemode create return processstuff stream continuation edit this section is an excerpt from continuation edit in computer science a continuation is an abstract representation of the control state of a computer program a continuation implements reifies the program control state i e the continuation is a data structure that represents the computational process at a given point in the process s execution the created data structure can be accessed by the programming language instead of being hidden in the runtime environment continuations are useful for encoding other control mechanisms in programming languages such as exceptions generators coroutines and so on the current continuation or continuation of the computation step is the continuation that from the perspective of running code would be derived from the current point in a program s execution the term continuations can also be used to refer to first class continuations which are constructs that give a programming language the ability to save the execution state at any point and return to that point at a later point in the program possibly multiple times generator edit this section is an excerpt from generator computer programming edit in computer science a generator is a routine that can be used to control the iteration behaviour of a loop all generators are also iterators 40 a generator is very similar to a function that returns an array in that a generator has parameters can be called and generates a sequence of values however instead of building an array containing all the values and returning them all at once a generator yields the values one at a time which requires less memory and allows the caller to get started processing the first few values immediately in short a generator looks like a function but behaves like an iterator generators can be implemented in terms of more expressive control flow constructs such as coroutines or first class continuations 41 generators also known as semicoroutines 42 are a special case of and weaker than coroutines in that they always yield control back to the caller when passing a value back rather than specifying a coroutine to jump to see comparison of coroutines with generators coroutine edit this section is an excerpt from coroutine edit coroutines are computer program components that can be suspended and resumed generalizing subroutines for cooperative multitasking coroutines are well suited for implementing familiar program components such as cooperative tasks exceptions event loops iterators infinite lists and pipes they have been described as functions whose execution you can pause 43 melvin conway coined the term coroutine in 1958 when he applied it to the construction of an assembly program 44 the first published explanation of the coroutine appeared later in 1963 45 comefrom edit this section is an excerpt from comefrom edit in computer programming comefrom is a control flow statement that causes control flow to jump to the statement after it when control reaches the point specified by the comefrom argument the statement is intended to be the opposite of goto and is considered to be more a joke than serious computer science often the specified jump point is identified as a label for example comefrom x specifies that when control reaches the label x then control continues at the statement after the comefrom a major difference with goto is that goto depends on the local structure of the code while comefrom depends on the global structure a goto statement transfers control when control reaches the statement but comefrom requires the processor i e interpreter to scan for comefrom statements so that when control reaches any of the specified points the processor can make the jump the resulting logic tends to be difficult to understand since there is no indication near a jump point that control will in fact jump one must study the entire program to see if any comefrom statements reference that point the semantics of a comefrom statement varies by programming language in some languages the jump occurs before the statement at the specified point is executed and in others the jump occurs after depending on the language multiple comefrom statements that reference the same point may be invalid non deterministic executed in some order or induce parallel or otherwise concurrent processing as seen in threaded intercal citation needed comefrom was initially seen in lists of joke assembly language instructions as cmfrm it was elaborated upon in a datamation article by r lawrence clark in 1973 46 written in response to edsger dijkstra s letter go to statement considered harmful comefrom was eventually implemented in the c intercal variant of the esoteric programming language intercal along with the even more obscure computed comefrom th...
|
