Every _BitInt(N) is a subtype of _BitInt(N+1). For practical purposes though, you'd usually make each intN a subtype of intN*2, up to some top integer type whic

Every _BitInt(N) is a subtype of _BitInt(N+1). For practical purposes though, you'd usually make each intN a subtype of intN*2, up to some top integer type which supports arbitrary precision. int8 <= int16 <= int32 <= int64 <= bigint For this mini subtype hierarchy, you can literally just number the types in increasing order, and use `<=`, rather than bitmasks. For inclusion of unsigned integers, the same rule applies, but each `unsigned _BitInt(N)` is also a subtype of `signed _BitInt(N+1)`. It might make sense to number the unsigned integers one higher than their signed variants of the same width to simplify testing for compatibility. A specific bit, such as 1000b could indicate a signed integer. UNSIGNED = 0000b; SIGNED = 1000b; enum IntType { UINT8 = UNSIGNED | 1, UINT16 = UNSIGNED | 2, UINT32 = UNSIGNED | 3, UINT64 = UNSIGNED | 4, UBIGINT = UNSIGNED | 7, INT8 = SIGNED | 0, INT16 = SIGNED | 1, INT32 = SIGNED | 2, INT64 = SIGNED | 3, BIGINT = SIGNED | 7, }; is_uint8_subtype(ty) = (ty | UNSIGNED) <= UINT8 is_uint16_subtype(ty) = (ty | UNSIGNED) <= UINT16 is_uint32_subtype(ty) = (ty | UNSIGNED) <= UINT32 is_uint64_subtype(ty) = (ty | UNSIGNED) <= UINT64 is_natural(ty) = (ty | UNSIGNED) <= UBIGINT is_int8_subtype(ty) = (ty | SIGNED) <= INT8 is_int16_subtype(ty) = (ty | SIGNED) <= INT16 is_int32_subtype(ty) = (ty | SIGNED) <= INT32 is_int64_subtype(ty) = (ty | SIGNED) <= INT64 is_integer(ty) = (ty | SIGNED) <= BIGINT This is approximately how I handle it the numerical tower in my interpreter (extended with some ad-hoc rules to also support rationals, real, complex and quaternions).