UnsameQ¶

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description¶

lhs =!= rhs or UnsameQ[lhs, rhs] is the negation of SameQ: True iff lhs and rhs are not structurally identical.

Examples (5)¶

Every input below was run against the current Mathilda build and its output recorded.

Basic examples (3)¶

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

In[2]:= FullForm[Hold[a =!= b =!= c]]
Out[2]= Hold[UnsameQ[a, b, c]]

In[3]:= 1 =!= 2 =!= 1
Out[3]= False

Applications (2)¶

In[4]:= a =!= b
Out[4]= True

In[5]:= a =!= a
Out[5]= False

Implementation notes¶

builtin_unsameq is the negation of structural identity over all argument pairs. With fewer than two arguments it returns True; otherwise it checks every pair (i,j) with expr_eq and returns False as soon as any two are structurally equal, else True. Like SameQ it uses no numeric coercion and always yields a definite boolean.

Attributes: Protected.

References¶

See also: SameQ

Source: src/comparisons.c
Specification: docs/spec/builtins/comparisons.md
Tests: tests/test_comparisons.c
Tests: tests/test_parse.c

Notes & additional examples¶

Notes¶

UnsameQ (=!=) is the structural negation of SameQ; it always decides to True or False.