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AddTo
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AddTo

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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

open allclose all

Basic Examples  (1)Summary of the most common use cases

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-ikq58e
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0e7pmhwp-d3oyff
Out[2]=2

Scope  (4)Survey of the scope of standard use cases

Add to a numerical value:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-3mn70w
Out[1]=1

Add to a symbolic value:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-2dqqdg
Out[1]=1

Add to all values in a list:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-boaay
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0e7pmhwp-2v76mu
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0e7pmhwp-koraoz
Out[3]=3

The first argument to AddTo need not be a symbol:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-5axyxt
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0e7pmhwp-s6reew
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0e7pmhwp-tck70d
Out[3]=3

Applications  (1)Sample problems that can be solved with this function

Find the first prime above one million:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-boq58a
Out[1]=1

Properties & Relations  (4)Properties of the function, and connections to other functions

AddTo is a short form of this assignment:

In[1]:=1
✖
https://wolfram.com/xid/0e7pmhwp-5h1xz5
Out[1]=1

PreIncrement is a special case of AddTo:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-lk1x9y
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0e7pmhwp-fbnbxw
Out[2]=2

SubtractFrom is closely related:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-c27up6
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0e7pmhwp-hrn14p
Out[2]=2

A related operation for lists is AppendTo:

In[1]:=1
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https://wolfram.com/xid/0e7pmhwp-uwb0lf
In[2]:=2
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https://wolfram.com/xid/0e7pmhwp-5o39k8
Out[2]=2

Possible Issues  (1)Common pitfalls and unexpected behavior

A variable to be incremented must have an initial value:

In[1]:=1
✖
https://wolfram.com/xid/0e7pmhwp-xd9vjs
Out[1]=1
Wolfram Research (1988), AddTo, Wolfram Language function, https://reference.wolfram.com/language/ref/AddTo.html.
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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.

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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.

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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

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

BibTeX

@misc{reference.wolfram_2025_addto, author="Wolfram Research", title="{AddTo}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/AddTo.html}", note=[Accessed: 24-March-2025 ]}

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@misc{reference.wolfram_2025_addto, author="Wolfram Research", title="{AddTo}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/AddTo.html}", note=[Accessed: 24-March-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_addto, organization={Wolfram Research}, title={AddTo}, year={1988}, url={https://reference.wolfram.com/language/ref/AddTo.html}, note=[Accessed: 24-March-2025 ]}

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@online{reference.wolfram_2025_addto, organization={Wolfram Research}, title={AddTo}, year={1988}, url={https://reference.wolfram.com/language/ref/AddTo.html}, note=[Accessed: 24-March-2025 ]}