pub const IUPAC_MASKS: [u8; 256];Expand description
ASCII-indexed IUPAC ambiguity masks. Bit 0 = A, bit 1 = C, bit 2 = G, bit 3 = T
(U is aliased to T). Case-insensitive: both uppercase and lowercase entries are
populated. Non-IUPAC bytes map to 0 — callers compute compatibility via
MASKS[a] & MASKS[b] != 0, and a 0 mask always yields “incompatible”.