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--x

decreases the value of x by 1, returning the new value of x.

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Basic Examples  
Scope  
Applications  
Properties & Relations  
Possible Issues  
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PreDecrement

--x

decreases the value of x by 1, returning the new value of x.

Details

Examples

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Basic Examples  (1)

Decrement the value by one and return the new value:

Wolfram Language code: k = 1;--k
Wolfram Language code: k

Scope  (4)

Decrement a numerical value:

Wolfram Language code: x = 1.5; --x;x

Decrement a symbolic value:

Wolfram Language code: v = a;--v;v

Decrement all values in a list:

Wolfram Language code: x = {1, 2, 3}
Wolfram Language code: --x;x

The argument to PreDecrement need not be a symbol:

Wolfram Language code: list = {1, 2, 3}
Wolfram Language code: --list[[2]]
Wolfram Language code: list

Applications  (1)

Find the first integer below one million with a certain property:

Wolfram Language code: i = 10 ^ 6; While[!PrimeQ[--i], Null]; i

Properties & Relations  (4)

Decrement and PreDecrement differ in the return value of the operation:

Wolfram Language code: {a, b} = {1, 1};
Wolfram Language code: {a--, --b}
Wolfram Language code: {a, b}

PreDecrement is a short form of this assignment:

Wolfram Language code: k = 1; k = k - 1

PreDecrement is a special case of SubtractFrom:

Wolfram Language code: k = 1; k -= 1

Increment and PreIncrement are closely related operations:

Wolfram Language code: {a, b, c, d} = {1, 1, 1, 1};
Wolfram Language code: {a++, ++b, c--, --d}
Wolfram Language code: {a, b, c, d}

Possible Issues  (1)

A variable to be decremented must have an initial value:

Wolfram Language code: --x
Wolfram Research (1988), PreDecrement, Wolfram Language function, https://reference.wolfram.com/language/ref/PreDecrement.html.

Text

Wolfram Research (1988), PreDecrement, Wolfram Language function, https://reference.wolfram.com/language/ref/PreDecrement.html.

CMS

Wolfram Language. 1988. "PreDecrement." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/PreDecrement.html.

APA

Wolfram Language. (1988). PreDecrement. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/PreDecrement.html

BibTeX

@misc{reference.wolfram_2026_predecrement, author="Wolfram Research", title="{PreDecrement}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/PreDecrement.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_predecrement, organization={Wolfram Research}, title={PreDecrement}, year={1988}, url={https://reference.wolfram.com/language/ref/PreDecrement.html}, note=[Accessed: 12-June-2026]}