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Complement

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Complement[all, $e_1$, $e_2$, ...]

returns an expression containing the elements in the set all that are not in any of $e_1$, $e_2$, etc.

Complement[all, $e_1$, $e_2$, ..., SameTest->test]

applies test to the elements in all and each of the ei to determine equality.

The sets all, $e_1$, etc can have any head, which must all match.

The returned expression has the same head as the input expressions. The expression will be sorted and each element will only occur once.

• • Complement[{a, b, c}, {a, c}]

• • Complement[{a, b, c}, {a, c}, {b}]

• • Complement[f[z, y, x, w], f[x], f[x, z]]

• • Complement[{c, b, a}]