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x+=dx

adds dx to x and returns the new value of x.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Applications  
Properties & Relations  
Possible Issues  
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Tech Notes
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AddTo

x+=dx

adds dx to x and returns the new value of x.

Details

  • x+=dx is equivalent to x=x+dx.
  • AddTo has the attribute HoldFirst.
  • In AddTo[x,f], x can be a symbol or other expression with an existing value. »

Examples

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Basic Examples  (1)

Wolfram Language code: k = 1;k += 5
Wolfram Language code: k

Scope  (4)

Add to a numerical value:

Wolfram Language code: x = 1.5; x += 3.75;x

Add to a symbolic value:

Wolfram Language code: v = a;v += b;v

Add to all values in a list:

Wolfram Language code: x = {1, 2, 3}
Wolfram Language code: x += 17;x
Wolfram Language code: x += {20, 21, 22};x

The first argument to AddTo need not be a symbol:

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

Applications  (1)

Find the first prime above one million:

Wolfram Language code: i = 10 ^ 6 - 1; While[!PrimeQ[i], i += 2]; i

Properties & Relations  (4)

AddTo is a short form of this assignment:

Wolfram Language code: k = 1; k = k + 5

PreIncrement is a special case of AddTo:

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

SubtractFrom is closely related:

Wolfram Language code: k = 10; k += -5
Wolfram Language code: k -= 5

A related operation for lists is AppendTo:

Wolfram Language code: list = {1, 2, 3};
Wolfram Language code: AppendTo[list, 4]; list

Possible Issues  (1)

A variable to be incremented must have an initial value:

Wolfram Language code: x += 2
Wolfram Research (1988), AddTo, Wolfram Language function, https://reference.wolfram.com/language/ref/AddTo.html.

Text

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

CMS

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

APA

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

BibTeX

@misc{reference.wolfram_2026_addto, author="Wolfram Research", title="{AddTo}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/AddTo.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_addto, organization={Wolfram Research}, title={AddTo}, year={1988}, url={https://reference.wolfram.com/language/ref/AddTo.html}, note=[Accessed: 12-June-2026]}