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Unevaluated

  • Unevaluated[ expr ] represents the unevaluated form of expr when it appears as the argument to a function.
  • f [Unevaluated[ expr ]] effectively works by temporarily setting attributes so that f holds its argument unevaluated, then evaluating f [ expr ].
  • Example: Length[Unevaluated[5+6]].
  • See the Mathematica book: Section 2.5.5.
  • See also: Hold, HoldFirst, ReplacePart.

    Further Examples

    The length of this unevaluated expression is 3.

    In[1]:=

    Out[1]=

    This can be seen more clearly from the internal representation of such expressions.

    In[2]:=

    Out[2]//FullForm=