WOLFRAM

Wolfram Language & System Documentation Center

Update[symbol]

tells the Wolfram Language that hidden changes have been made that could affect values associated with a symbol.

Update[]

specifies that the value of any symbol could be affected.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
See Also
Tech Notes
Related Guides
History
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Update

Update[symbol]

tells the Wolfram Language that hidden changes have been made that could affect values associated with a symbol.

Update[]

specifies that the value of any symbol could be affected.

Details

  • Update manipulates internal optimization features of the Wolfram Language. It should not need to be called except under special circumstances that rarely occur in practice.
  • One special circumstance is that changes in the value of one symbol can affect the value of another symbol by changing the outcome of Condition tests. In such cases, you may need to use Update on the symbol you think may be affected.
  • Using Update will never give you incorrect results, although it will slow down the operation of the system.

Examples

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Basic Examples  (1)

Make sure that values that depend on f are returned correctly:

Wolfram Language code: f[] /; g := 1;

The value of t depends on the definitions for f:

Wolfram Language code: t = f[];
Wolfram Language code: t

Now change the value of g that f, in turn, depends on:

Wolfram Language code: g = True;

The value of t is still based on the old value of f that was correct before g was changed:

Wolfram Language code: t

But the value of f[] has changed:

Wolfram Language code: f[]

Tell the Wolfram Language that changes have been made affecting values that depend on f:

Wolfram Language code: Update[f]

Now the value of t returns as expected:

Wolfram Language code: t

Scope  (1)

Create a symbol t that depends on two symbols, f and g:

Wolfram Language code: f[] /; h = 1; g[] /; h = 2; t = {f[], g[]}

The implicit dependence of t on h is missed by normal evaluation:

Wolfram Language code: h = True;t

Update all implicit dependencies:

Wolfram Language code: Update[]

The value of t has been updated:

Wolfram Language code: t

Note that t is still defined in terms of f and g:

Wolfram Language code: t//OwnValues
Wolfram Research (1988), Update, Wolfram Language function, https://reference.wolfram.com/language/ref/Update.html.

Text

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

CMS

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

APA

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

BibTeX

@misc{reference.wolfram_2026_update, author="Wolfram Research", title="{Update}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/Update.html}", note=[Accessed: 13-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_update, organization={Wolfram Research}, title={Update}, year={1988}, url={https://reference.wolfram.com/language/ref/Update.html}, note=[Accessed: 13-June-2026]}