Function complexIterator

src/compute-engine/library/sets.ts:1439–1454

(
  self: Expression
)

  const typeName = sym(collection);
  if (typeName) {
    // 3. Type-style membership, e.g. Element(x, finite_real)
    try {
      const type = ce.type(typeName);
      if (!type.isUnknown) {
        // Three-valued: in particular, a concrete number literal whose type
        // overlaps but does not match is definitively excluded (e.g.
        // `Element(2.5, integer)` → False, even though
        // `finite_rational ∩ integer` is non-empty), while a symbol of
        // overlapping type stays indeterminate (falls through).
        const r = typeMembership(x, type.type);
        if (r !== undefined) return r;
      }
    } catch {
      // If type parsing fails (e.g., "Booleans" is not a valid type),
      // fall through
    }

    // 4. Primitive number-set symbols map to types (query-side mirror of
    //    the assume-side refinement)