Orderless

Orderless

is an attribute indicating that the leaves in an expression f(a, b, c) can be placed in any order.

See

The leaves of an Orderless function are automatically sorted:

>> SetAttributes(f, Orderless)
>> f(c, a, b, a + b, 3, 1.0)
f(1.0,3,a,b,a+b,c)

A symbol with the Orderless attribute represents a commutative mathematical operation.

>> f(a, b) == f(b, a)
True

Orderless affects pattern matching:

>> SetAttributes(f, Flat)
>> f(a, b, c) /. f(a, c) -> d
f(b, d)