This is documentation for Mathematica 3, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.1)
 Documentation / Mathematica / Built-in Functions / Programming / Tests  /
ValueQ

  • ValueQ[ expr ] gives True if a value has been defined for expr, and gives False otherwise.
  • ValueQ has attribute HoldFirst.
  • ValueQ gives False only if expr would not change if it were to be entered as Mathematica input.
  • See the Mathematica book: Section 2.3.5.
  • See also: Information.

    Further Examples

    At the start of a new session, no values have been defined for symbols such as xx.

    In[1]:=

    Out[1]=

    In[2]:=

    Out[2]=

    In[3]:=

    Out[3]=

    In[4]:=

    In[5]:=

    Out[5]=