Usage

R:=set/element-of(x, S)R:=x∈S

Description

Determines whether an element x is a member of set S.

This function returns a boolean value indicating whether x exists within the set.

It wraps Rust's IndexSet membership check, returning true if the element is found.

Input

Arguments:

• x : T — the element being tested for membership.

• S : set of T — the set to test against.

Element type constraints:

• T must be hashable and comparable for equality (Eq + Hash in Rust).

• Common scalar kinds: integers, strings, symbols, booleans.

Output

Result:

• R : boolean — true if x is an element of S, otherwise false.

Examples

True — element is in the set

False — element not in the set

Symbols or strings

Details

Set semantics:

• The set treats elements as unique based on hash and equality.

• Duplicates are ignored in the set.

Relation logic:

• Returns true if the element exists in the set.

Symbolic shorthand:

• x ∈ S is equivalent to set/element-of(x, S).

Performance:

• Average O(1) time per lookup using hashing.

Determinism:

• Results are deterministic across runs and platforms.

Errors

• Incorrect number of arguments (expects two).

• Unsupported element type (not hashable or comparable).

• Type mismatch between x and elements of S.