Mathematics to code : ∈

x is an element of A



R function : x ∈ A?

is.element(x, A)

Python operator : x ∈ A?

x in A

Ruby method : x ∈ A?

A.include?x

JavaScript expression or method : x ∈ A?

A.indexOf(x) != -1
A.includes(x) // ES2016+
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