DiscreteIndicator

DiscreteIndicator[x, x1, {u1, u2, ...}] yields the discrete indicator function, equal to 1 if x=x1 and, otherwise, to 0 if x=ui for some i.

Examples

DiscreteIndicator[a, a, {a, b, c}]
(* 1 *)

DiscreteIndicator[b, a, {a, b, c}]
(* 0 *)

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