OptionalElement

OptionalElement[patt]

is a grammar rules pattern object that represents 0 or 1 instances of patt.

OptionalElement[patt,default]

uses default if the element is not present.

Details

Examples

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Basic Examples  (2)

Allow certain words to be optional:

In[1]:=
Click for copyable input
Out[1]=
In[2]:=
Click for copyable input
Out[2]=

Supply a default value for a missing element:

In[1]:=
Click for copyable input
Out[1]=
In[2]:=
Click for copyable input
Out[2]=
In[3]:=
Click for copyable input
Out[3]=

Possible Issues  (1)

See Also

GrammarRules  GrammarApply  Repeated  Optional  FixedOrder

Introduced in 2015
(10.1)