! @abstract Table for converting a nucleotide character to 4-bit encoding.
The input character may be either an IUPAC ambiguity code, '=' for 0, or
'0'/'1'/'2'/'3' for a result of 1/2/4/8. The result is encoded as 1/2/4/8
for A/C/G/T or combinations of these bits for ambiguous bases.
! @abstract Table for converting a nucleotide character to 4-bit encoding. The input character may be either an IUPAC ambiguity code, '=' for 0, or '0'/'1'/'2'/'3' for a result of 1/2/4/8. The result is encoded as 1/2/4/8 for A/C/G/T or combinations of these bits for ambiguous bases.