SameQ

lhs === rhs evaluates to True if lhs and rhs are identical after evaluation, False otherwise.

Attributes[SameQ] := {Protected}

Simple examples

In[1]:= a===a
Out[1]= True

In[2]:= 5 === 5
Out[2]= True

Unlike Equal, SameQ does not forgive differences between Integers and Reals:

In[3]:= 5 === 5.
Out[3]= False

SameQ considers the arguments of all expressions and subexpressions:

In[4]:= foo[x == 2, y, x] === foo[x == 2, y, x]
Out[4]= True

In[5]:= foo[x == 2, y, x] === foo[x == 2., y, x]
Out[5]= False

Further examples

SameQ does not match patterns:

In[1]:= {1, 2, 3} === _List
Out[1]= False

This functionality is reserved for MatchQ:

In[2]:= MatchQ[{1, 2, 3}, _List]
Out[2]= True