Defer

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`Defer`

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Defer[expr]

yields an object that displays as the unevaluated form of expr, but that is evaluated if it is explicitly given as Wolfram Language input.

Details

Defer[expr] returns an object that remains unchanged until it is explicitly supplied as Wolfram Language input and evaluated using , Evaluate in Place, etc.
Defer gives an object whose evaluation is merely deferred until it is explicitly given as Wolfram Language input; HoldForm gives an object that is never evaluated.
If an object contains several levels of nested Defer constructs, one level is removed each time the object is evaluated as Wolfram Language input.
Defer prevents evaluation, not formatting. Objects such as Grid and Manipulate will still format in StandardForm in the usual way when wrapped in Defer.

Examples

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Basic Examples (2)Summary of the most common use cases

By default, arguments are evaluated:

In[1]:=1

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https://wolfram.com/xid/0mrc1g-lipmex

Out[1]=1

Use Defer to display an unevaluated form:

In[2]:=2

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https://wolfram.com/xid/0mrc1g-suf4b

Out[2]=2

Copy the previous output and evaluate:

In[3]:=3

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https://wolfram.com/xid/0mrc1g-buce3d

Out[3]=3

Use Defer to create cells with unevaluated contents:

In[1]:=1

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https://wolfram.com/xid/0mrc1g-g49j5n

In[2]:=2

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https://wolfram.com/xid/0mrc1g-jx77f

In[3]:=3

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https://wolfram.com/xid/0mrc1g-nv5ifn

In[4]:=4

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https://wolfram.com/xid/0mrc1g-j6an9u

In[5]:=5

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https://wolfram.com/xid/0mrc1g-iv7tb4

In[6]:=6

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https://wolfram.com/xid/0mrc1g-fwguh6

Properties & Relations (1)Properties of the function, and connections to other functions

Use HoldForm to display in unevaluated form:

In[1]:=1

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https://wolfram.com/xid/0mrc1g-onz6n3

Out[1]=1

Copy the output and evaluate; the result stays unevaluated:

In[2]:=2

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https://wolfram.com/xid/0mrc1g-bk3hu8

Out[2]=2

Use ReleaseHold to force evaluation of the result:

In[3]:=3

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https://wolfram.com/xid/0mrc1g-cjrwc

Out[3]=3

Use Defer to display in unevaluated form:

In[4]:=4

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https://wolfram.com/xid/0mrc1g-jhuw9q

Out[4]=4

Copy the output and evaluate:

In[5]:=5

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https://wolfram.com/xid/0mrc1g-hlrbb6

Out[5]=5

Possible Issues (1)Common pitfalls and unexpected behavior

Defer prevents evaluation, not typesetting:

In[1]:=1

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https://wolfram.com/xid/0mrc1g-75o7ig

Use InputForm or ToString to prevent typesetting:

In[2]:=2

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https://wolfram.com/xid/0mrc1g-14j59e

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