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following causes of side effects through a function call: 1. Performing I/O. 2. Modifying global variables. 3. Modifying local permanent variables (like static variables in C). 4. Modifying an argument passed by reference. 5. Modifying a local variable, either automatic or static, of a function higher up in the function call sequence (usually via a pointer).
71:; or calling other functions with side-effects. In the presence of side effects, a program's behaviour may depend on history; that is, the order of evaluation matters. Understanding and debugging a function with side effects requires knowledge about the context and its possible histories. Side effects play an important role in the design and analysis of
667:
The term Side effect refers to the modification of the nonlocal environment. Generally this happens when a function (or a procedure) modifies a global variable or arguments passed by reference parameters. But here are other ways in which the nonlocal environment can be modified. We consider the
184:
Side effects caused by the time taken for an operation to execute are usually ignored when discussing side effects and referential transparency. There are some cases, such as with hardware timing or testing, where operations are inserted specifically for their temporal side effects e.g.
140:
with hidden side effects is that, if many instructions have side effects on a single piece of state, like condition codes, then the logic required to update that state sequentially may become a performance bottleneck. The problem is particularly acute on some processors designed with
211:
with side effects is idempotent if multiple applications of the subroutine have the same effect on the system state as a single application, in other words if the function from the system state space to itself associated with the subroutine is idempotent in the
163:
Absence of side effects is a necessary, but not sufficient, condition for referential transparency. Referential transparency means that an expression (such as a function call) can be replaced with its value. This requires that the expression is
127:
side effects—instructions that modify parts of the processor state which are not mentioned in the instruction's mnemonic. A classic example of a hidden side effect is an arithmetic instruction that implicitly modifies
55:
if it has any observable effect other than its primary effect of reading the value of its arguments and returning a value to the invoker of the operation. Example side effects include modifying a
823:
149:. Such a processor may require additional control circuitry to detect hidden side effects and stall the pipeline if the next instruction depends on the results of those effects.
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775:. Conference Record of the 20th Annual ACM Symposium on Principles of Programming Languages. pp. 71–84.
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to the return value of the first application to -3 returns the same value as the first application to -3.
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was already set to 3 after the first application, and it is still set to 3 after the second application.
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75:. The degree to which side effects are used depends on the programming paradigm. For example,
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aims to minimize or eliminate side effects. The lack of side effects makes it easier to do
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193:. These instructions do not change state other than taking an amount of time to complete.
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is commonly used to produce side effects, to update a system's state. By contrast,
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do not restrict side effects, but it is customary for programmers to avoid them.
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is commonly used to report on the state of system, without side effects.
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591:// b = 3 evaluates to 3, which then casts to true so the loop is infinite
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This presents a potential hangup for novice programmers who may confuse
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to 3 has the same effect on the system state as the first application:
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is an expression that evaluates to the same value as the expression
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One common demonstration of side effect behavior is that of the
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27:
Of a function, an additional effect besides returning a value
647:
Spuler, David A.; Sajeev, A. Sayed
Muhammed (January 1994).
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1368:
32:"Hidden side effect" redirects here. For similar uses, see
757:
68:
1383:
794:
336:. For instance, consider the following Python program:
101:
and other stateful computations by replacing them with
500:// b = 3 evaluates to 3, which then gets assigned to a
132:(a hidden side effect) while it explicitly modifies a
136:(the intended effect). One potential drawback of an
640:
1499:
764:
649:Compiler Detection of Function Call Side Effects
430:is idempotent because the second application of
317:is idempotent because the second application of
824:
779:
729:"CSc 520 Principles of Programming Languages"
720:
646:
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603:Action at a distance (computer programming)
203:Idempotence § Computer science meaning
152:
67:; raising errors or exceptions; performing
1482:
1472:
831:
817:
771:Jones, Simon Peyton; Wadler, Phil (1993).
673:
176:for the same input) and side-effect free.
789:; Findler, Robert Bruce; Flatt, Matthew;
685:Research Topics in Functional Programming
660:
332:is idempotent if it is idempotent in the
726:
179:
168:, that is to say the expression must be
216:. For instance, consider the following
14:
1500:
679:
458:, with the side effect of storing the
105:actions. Functional languages such as
93:of a program. The functional language
812:
727:Collberg, Christian S. (2005-04-22).
191:for (int i = 0; i < 10000; ++i) {}
838:
697:"Why Functional Programming Matters"
474:. This allows multiple assignment:
24:
731:. Department of Computer Science,
694:
25:
1529:
773:Imperative Functional Programming
1481:
1471:
1462:
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97:eliminates side effects such as
34:hidden variable (disambiguation)
709:from the original on 2022-06-14
196:
18:Side-effect (computer science)
13:
1:
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123:programmers must be aware of
560:// tests if b evaluates to 3
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1513:Programming language theory
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795:"How To Design Programs"
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509:, this is equivalent to
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159:Referential transparency
153:Referential transparency
1034:Abstract interpretation
81:declarative programming
1518:Functional programming
791:Krishnamurthi, Shriram
172:(always give the same
147:out-of-order execution
87:Functional programming
77:imperative programming
63:or a mutable argument
943:Categorical semantics
733:University of Arizona
653:James Cook University
628:Unspecified behaviour
505:Because the operator
180:Temporal side effects
145:(since 1990) or with
73:programming languages
61:static local variable
1508:Computer programming
889:Runtime verification
1146:Invariant inference
894:Safety and liveness
787:Felleisen, Matthias
758:"Haskell 98 report"
623:Undefined behaviour
618:Side-channel attack
444:assignment operator
91:formal verification
65:passed by reference
1310:Constraint solvers
1136:Concolic execution
1091:Symbolic execution
899:Undefined behavior
854:Control-flow graph
334:mathematical sense
214:mathematical sense
57:non-local variable
51:is said to have a
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691:. pp. 17–42.
450:. The assignment
121:Assembly language
16:(Redirected from
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735:. Archived from
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681:Turner, David A.
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797:(2 ed.).
793:(2014-08-01).
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695:Hughes, John.
689:Addison-Wesley
683:, ed. (1990).
672:
662:10.1.1.70.2096
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613:Sequence point
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201:Main article:
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1247:Incorrectness
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1214:Specification
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1066:Effect system
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1000:State machine
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739:on 2022-08-06
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330:pure function
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35:
30:
19:
1409:Isabelle/HOL
1226:Verification
1209:completeness
1199:
1101:Type systems
1044:Control flow
938:Denotational
879:Polyvariance
847:Key concepts
781:
772:
766:
752:
741:. Retrieved
737:the original
722:
711:. Retrieved
684:
675:
666:
648:
642:
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533:
504:
441:
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327:
313:
206:
183:
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124:
119:
85:
52:
38:
29:
1338:Lightweight
1200:Side effect
1096:Termination
950:Operational
859:Correctness
197:Idempotence
187:sleep(5000)
107:Standard ML
53:side effect
1502:Categories
1293:Union-find
1257:Separation
1195:Refinement
1061:Dependence
960:Small-step
869:Invariants
743:2022-08-06
713:2022-08-06
634:References
209:subroutine
143:pipelining
49:expression
1389:HOL Light
1219:Languages
1205:Soundness
1124:Data-flow
1106:Typestate
1056:Data-flow
985:Petri net
933:Axiomatic
918:Semantics
799:MIT Press
657:CiteSeerX
466:into the
220:program:
1487:Glossary
1467:Category
1404:Isabelle
1288:Hashcons
1262:Temporal
1178:Concepts
1018:Analyses
955:Big-step
704:Archived
597:See also
134:register
45:function
1477:Outline
1283:E-graph
1156:Testing
1141:Fuzzing
1116:Dynamic
1081:Pointer
760:. 1998.
468:L-value
460:R-value
438:Example
103:monadic
95:Haskell
1252:Linear
1235:Logics
1071:Escape
1026:Static
972:Models
659:
383:assert
356:return
300:assert
276:assert
249:global
218:Python
125:hidden
111:Scheme
1441:Twelf
1431:NuPRL
1426:Mizar
1399:Idris
1346:Alloy
1302:Tools
1242:Hoare
1086:Shape
1039:Alias
926:Types
707:(PDF)
700:(PDF)
570:while
565:with
539:while
452:a = b
174:value
115:Scala
1421:LEGO
1416:Lean
1394:HOL4
1374:Agda
1369:ACL2
1351:TLA+
1207:and
1049:kCFA
693:Via
377:else
371:<
319:setx
315:setx
288:setx
264:setx
237:setx
166:pure
113:and
59:, a
1436:PVS
1379:Coq
1328:SMT
1323:SAT
1318:CHC
1278:BDD
470:of
462:of
446:in
432:abs
428:abs
410:abs
392:abs
386:abs
344:abs
341:def
234:def
189:or
99:I/O
69:I/O
47:or
39:In
1504::
1384:F*
702:.
687:.
665:.
655:.
651:.
588:{}
557:{}
548:==
497:);
407:==
404:))
365:if
353:):
328:A
306:==
282:==
246:):
207:A
109:,
832:e
825:t
818:v
801:.
746:.
716:.
585:)
582:3
579:=
576:b
573:(
554:)
551:3
545:b
542:(
529:;
526:3
523:=
520:b
517:=
514:a
494:3
491:=
488:b
485:(
482:=
479:a
472:a
464:b
456:b
448:C
422:)
419:3
416:-
413:(
401:3
398:-
395:(
389:(
380:n
374:0
368:n
362:n
359:-
350:n
347:(
323:x
309:3
303:x
297:)
294:3
291:(
285:3
279:x
273:)
270:3
267:(
261:n
258:=
255:x
252:x
243:n
240:(
231:0
228:=
225:x
36:.
20:)
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