Hi. Does anyone know why -type dna_nucleotide() :: $G | $C | $T | $A. is not valid sytax, while -type dna_nucleotide() :: 71 | 67 | 84 | 65. of course is? mr -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://erlang.org/pipermail/erlang-questions/attachments/20161015/2505ae6f/attachment.htm>