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often guess that they were created to use the auto-increment and auto-decrement address modes provided by the DEC PDP-11 on which C and Unix first became popular. This is historically impossible, since there was no PDP-11 when B was developed. The PDP-7, however, did have a few 'auto-increment' memory cells, with the property that an indirect memory reference through them incremented the cell. This feature probably suggested such operators to
Thompson; the generalization to make them both prefix and postfix was his own. Indeed, the auto-increment cells were not used directly in implementation of the operators, and a stronger motivation for the innovation was probably his observation that the translation of ++x was smaller than that of x=x+1.
36:
246:
the "next" (or "previous") item of that array. Thus, incrementing a pointer to an integer makes it point to the next integer (typically increasing the pointer value by 4); incrementing a pointer to a structure of size 106 bytes makes it point to the next structure by increasing the pointer value by 106.
245:
In languages with typed pointers like C, the increment operator steps the pointer to the next item of that type -- increasing the value of the pointer by the size of that type. When a pointer (of the right type) points to any item in an array, incrementing (or decrementing) makes the pointer point to
1079:
Thompson went a step further by inventing the ++ and -- operators, which increment or decrement; their prefix or postfix position determines whether the alteration occurs before or after noting the value of the operand. They were not in the earliest versions of B, but appeared along the way. People
234:
Since the increment/decrement operator modifies its operand, use of such an operand more than once within the same expression can produce undefined results. For example, in expressions such as
53:
1232:
898:
The following list, though not complete or all-inclusive, lists some of the major programming languages that support the increment and decrement operators.
208:-decrement operators increment (or decrement) their operand by 1, and the value of the expression is the resulting incremented (or decremented) value.
1302:
100:
182:
The increment operator increases, and the decrement operator decreases, the value of its operand by 1. The operand must have an arithmetic or
72:
1372:
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193:. Pointers values are increased (or decreased) by an amount that makes them point to the next (or previous) element adjacent in memory.
1216:
1146:
219:-decrement operators increase (or decrease) the value of their operand by 1, but the value of the expression is the operand's value
119:
238:, it is not clear in what sequence the subtraction and increment operations should be performed. Such expressions generally invoke
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once supported these operators, but they have been depreciated since version 2.2 and removed as of version 3.0.
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164:-like languages feature two versions (pre- and post-) of each operator with slightly different semantics.
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In languages lacking these operators, equivalent results require an extra line of code:
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171:(including C and its various derivatives), the increment operator is written as
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390:// Post-decrement: y is assigned the value of x, then x is decremented by 1
321:// Post-increment: y is assigned the value of x, then x is incremented by 1
1419:
357:// Pre-decrement: x is decremented by 1, then y is assigned the value of x
288:// Pre-increment: x is incremented by 1, then y is assigned the value of x
1033:
27:
Unary operators that add or subtract one from their operand, respectively
231:), only one version is needed (in the case of Go, post operators only).
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The following C code fragment illustrates the difference between the
1207:(2. ed., ed.). Englewood Cliffs, N.J.: Prentice Hall. p.
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756:
227:
In languages where increment/decrement is not an expression (e.g.,
1104:
1199:
Ritchie, Brian W. Kernighan; Dennis M.; Ritchie, Dennis (1988).
980:
985:
907:
835:// this statement displays 2, then c is incremented by 1 to 3.
457:# x is now 2 (can be written as "x += 1" in Python)
29:
901:
755:
These examples also work in other C-like languages, such as
179:. Several other languages use inc(x) and dec(x) functions.
196:
In languages that support both versions of the operators:
859:// this statement increments c by 1, then c is displayed.
639:
The post-increment operator is also commonly used with
771:
Increment operator can be demonstrated by an example:
60:. Unsourced material may be challenged and removed.
1200:
517:The post-increment operator is commonly used with
8:
1231:: CS1 maint: multiple names: authors list (
223:to the increment (or decrement) operation.
1418:
175:and the decrement operator is written as
120:Learn how and when to remove this message
1333:. Wolfram Language Documentation Center.
1319:. Wolfram Language Documentation Center.
167:In languages syntactically derived from
1186:"8.3. The Double-Parentheses Construct"
1126:
717:// Loop that counts down from n to zero
1224:
7:
1135:"Understanding and Using C Pointers"
58:adding citations to reliable sources
1403:"The Development of the C Language"
1331:"Decrement Wolfram Language Symbol"
1317:"Increment Wolfram Language Symbol"
1289:"GP Operators and their Priorities"
744:// Copies element *(src) to *(dst),
622:// through n elements of the array
619:// Post-increment of i, which steps
262:increment and decrement operators:
69:"Increment and decrement operators"
1188:. The Linux Documentation Project.
1067:The concept was introduced in the
25:
747:// then increments both pointers
189:, and must refer to a modifiable
1139:"Chapter 4. Pointers and Arrays"
1059:do not support these operators.
146:that increase or decrease their
34:
1247:"Increment/decrement operators"
526:// Sum the elements of an array
45:needs additional citations for
1263:. Microsoft Developer Network.
1:
1141:. O'Reilly Media, Inc. 2013.
1000:Vex, a scripting language in
1303:"About Assignment Operators"
1261:"++ Operator (C# Reference)"
648:// Copy one array to another
1345:"New Features in Swift 2.2"
1174:. Free Software Foundation.
153:They are commonly found in
1462:
1203:The C programming language
387:// x is now 0, y is also 0
318:// x is now 2, y is also 2
1361:. Swift Official Website.
1347:. Swift Official Website.
1159:"Introductory C with C++"
521:subscripts. For example:
472:# Post-increment: y = x++
242:, and should be avoided.
1048:) instead of operators.
878:
772:
645:
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430:# Pre-increment: y = ++x
427:
264:
1441:Operators (programming)
1275:"Operator Overloading"
1172:"GNU Awk's User Guide"
1082:
1069:B programming language
354:// Decrement operators
285:// Increment operators
1420:10.1145/155360.155580
1359:"Swift 3.0 Released!"
1161:. 2019. Figure 12-12.
1077:
420:// y is 1, x is now 0
351:// y is 1, x is now 2
158:programming languages
1091:Augmented assignment
894:Supporting languages
54:improve this article
1407:ACM SIGPLAN Notices
1249:. cppreference.com.
137:decrement operators
1399:Ritchie, Dennis M.
1157:Richard Petersen.
1115:Successor function
240:undefined behavior
18:Increment operator
1133:Richard M Reese.
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65:Find sources:
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1277:. dlang.org.
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52:Please help
47:verification
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962:Objective-C
191:data object
1435:Categories
1381:operators"
1121:References
991:PowerShell
967:GNU Octave
957:JavaScript
654:copy_array
155:imperative
80:newspapers
1227:cite book
1101:operators
187:data type
150:by one.
144:operators
133:Increment
1413:(3): 5.
1085:See also
1051:Notably
1034:Modula-2
1018:Apple's
814:"%d
775:#include
641:pointers
493:# y is 1
250:Examples
1063:History
1002:Houdini
972:PARI/GP
877:Output:
236:x - ++x
184:pointer
148:operand
94:scholar
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1110:PDP-11
1093:– for
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1046:dec(x)
1042:inc(x)
1038:Oberon
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862:return
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529:float
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141:unary
101:JSTOR
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217:post
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574:int
568:0.0
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270:x
169:B
162:C
123:)
117:(
112:)
108:(
98:·
91:·
84:·
77:·
50:.
20:)
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