Version 0.3: Might change, but is usable just fine
Beta is a library for converting TypeGreek-flavoured Betacode to polytonic Greek. It can generate UTF-8 text with precomposed characters (NFC) or combining diacritics (NFD). Read this Go blog entry for more information about text normalisation.
This implementation is independent of TypeGreek, but implements the same rules: diacritics can appear in any order after the base character, capital Betacode letters form capital Greek letters (no asterisk), and a sigma followed by whitespace or punctuation becomes a terminal sigma automatically.
Sort-of parsing the Greek subset of Standard Betacode is now implemented. This means interpreting asterisks and putting up with diacritics after the asterisk and before the base character, but unlike Standard Betacode, this implementation is never case-insensitive.
The directory beta contains a minimal example program that uses beta.Writer.