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Evaluate
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Evaluate

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Evaluate[expr]

causes expr to be evaluated even if it appears as the argument of a function whose attributes specify that it should be held unevaluated.

Details

  • You can use Evaluate to override HoldFirst etc. attributes of built‐in functions.
  • Evaluate only overrides HoldFirst etc. attributes when it appears directly as the head of the function argument that would otherwise be held. »

Examples

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

Evaluate inside a Hold:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-dgjw5r
Out[1]=1

Scope  (1)Survey of the scope of standard use cases

Evaluate works for arguments of any symbol with attributes HoldAll, HoldFirst, or HoldRest:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-ew22wx
Out[1]=1

Since Attributes is HoldAll, use Evaluate to find the properties of the value of x:

In[2]:=2
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https://wolfram.com/xid/0bn6gs0-noi1g
In[3]:=3
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https://wolfram.com/xid/0bn6gs0-flg7j6
Out[3]=3

Applications  (3)Sample problems that can be solved with this function

Unprotect a system symbol to make a definition for it:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-o91jzh
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bn6gs0-dxfo8h

Restore protection:

In[3]:=3
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https://wolfram.com/xid/0bn6gs0-bojqmk
Out[3]=3

Force evaluation of the right-hand side of a delayed definition:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-lrcr7t
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bn6gs0-istkrz
In[3]:=3
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https://wolfram.com/xid/0bn6gs0-bmqyvi
Out[3]=3

Build a function from an expression:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-g54vrj
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bn6gs0-bu71nd
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bn6gs0-mfi9lt
Out[3]=3

Properties & Relations  (3)Properties of the function, and connections to other functions

Evaluate does not work inside functions with attribute HoldAllComplete:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-j237h
Out[1]=1

Use Unevaluated to temporarily treat a function as if it were HoldAll:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-dddjpx
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bn6gs0-djmcrk
Out[2]=2

Evaluate does not work inside Unevaluated:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-bkju4t
Out[1]=1

Possible Issues  (1)Common pitfalls and unexpected behavior

Evaluate works only on the first level, directly inside a held function:

In[1]:=1
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https://wolfram.com/xid/0bn6gs0-fcqyyp
Out[1]=1
Wolfram Research (1991), Evaluate, Wolfram Language function, https://reference.wolfram.com/language/ref/Evaluate.html.
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Wolfram Research (1991), Evaluate, Wolfram Language function, https://reference.wolfram.com/language/ref/Evaluate.html.

Text

Wolfram Research (1991), Evaluate, Wolfram Language function, https://reference.wolfram.com/language/ref/Evaluate.html.

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Wolfram Research (1991), Evaluate, Wolfram Language function, https://reference.wolfram.com/language/ref/Evaluate.html.

CMS

Wolfram Language. 1991. "Evaluate." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Evaluate.html.

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Wolfram Language. 1991. "Evaluate." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Evaluate.html.

APA

Wolfram Language. (1991). Evaluate. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Evaluate.html

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Wolfram Language. (1991). Evaluate. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Evaluate.html

BibTeX

@misc{reference.wolfram_2025_evaluate, author="Wolfram Research", title="{Evaluate}", year="1991", howpublished="\url{https://reference.wolfram.com/language/ref/Evaluate.html}", note=[Accessed: 11-May-2025 ]}

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@misc{reference.wolfram_2025_evaluate, author="Wolfram Research", title="{Evaluate}", year="1991", howpublished="\url{https://reference.wolfram.com/language/ref/Evaluate.html}", note=[Accessed: 11-May-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_evaluate, organization={Wolfram Research}, title={Evaluate}, year={1991}, url={https://reference.wolfram.com/language/ref/Evaluate.html}, note=[Accessed: 11-May-2025 ]}

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@online{reference.wolfram_2025_evaluate, organization={Wolfram Research}, title={Evaluate}, year={1991}, url={https://reference.wolfram.com/language/ref/Evaluate.html}, note=[Accessed: 11-May-2025 ]}