WolframLang: Equality Test

By Xah Lee. Date: . Last updated: .

Tip on equality test

SameQ[expr1, expr2]
(short syntax: ===)

return True if two expressions are symbolically identical, else False.

examples:

  • {a,b,c} === {a,b,c} return True because they are the same expression term-by-term.
  • 3 === 3.0 return False because one is exact number while the other is approx.
  • 3 === xyz return False because xyz is a symbol. (unless it has a value of 3)
SameQ
x = 3;
y = 3.0;
x === y
(* False *)
Equal[expr1, expr2]
(short syntax: ==)
  • return True if two expressions are semantically equal. (e.g. 3 vs 3.0)
  • return False if two expressions are not semantically equal.
  • return whole expression as is, if semantic equality cannot be determined easily or WolframLang quirk.

Equal

3 == 3
(* True *)

3 == 3.0
(* True *)

{3} == {3.0}
(* True *)

WARNING. Equal does not return True or False even for obvious cases.

{} == 2
(* return expression as is *)

Reduce[ {} == 2 ]
(* but this is now True *)
(* WARNING *)
{{1}} == {2}
(* return expression as is *)

{{1.0}} == {2.0}
(* return expression as is *)
WolframLang equality bug 2022-09-18 k93F6
WolframLang equality issue 2022-09-18
x == 3
(* return as is *)

ReplaceAll[ x == 3 , x -> 3 ]
(* True *)

Inequality

UnsameQ
(short syntax: =!=)
Same as Not[SameQ[x, y]] . UnsameQ
Unequal
(short syntax: !=)
Same as Not[Equal[x, y]]. Unequal

WolframLang Boolean

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