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Further Examples: Unevaluated

Unevaluated stops Plus from evaluating its arguments so the result is Plus. Unevaluated is transparent to Head.

In[1]:=

Out[1]=

Here the arguments are evaluated so the result is no longer Plus.

In[2]:=

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The algebraic expression remains unevaluated so terms with head Integer, Rational, or Real are returned.

In[3]:=

Out[3]=

Here the algebraic expression evaluates to a complex number, so there are no terms left with the specified heads.

In[4]:=

Out[4]=

See also the Further Examples for Function.