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Putting Constraints on Patterns
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ValueQ
ValueQ
[
expr
]
gives
True
if a value has been defined for
expr
, and gives
False
otherwise.
MORE INFORMATION
ValueQ
has attribute
HoldFirst
.
ValueQ
gives
False
only if
expr
would not change if it were to be entered as
Mathematica
input.
EXAMPLES
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Basic Examples
(2)
In[1]:=
Out[1]=
In[2]:=
In[3]:=
Out[3]=
Only the one argument form of
f
has values associated with it:
In[1]:=
In[2]:=
Out[2]=
In[3]:=
Out[3]=
Scope
(3)
Properties & Relations
(2)
Possible Issues
(1)
SEE ALSO
Information
TUTORIALS
Putting Constraints on Patterns
MORE ABOUT
Symbol Handling
New in 1
© 2008 Wolfram Research, Inc.
EXAMPLES
Basic Examples 
Scope