What do Erlang release numbers mean?

Question

I've noticed Erlang releases with version numbers like R13B04, R14B, R15A, etc. What do each of the release number components mean? Can one infer anything about API changes based on the version numbers? For example, does an upgrade from R13 to R14 imply backwards incompatible API changes?

Answer 1

For example R14B04. R stands for Erlang/OPT Release. 14 is major version number. B stands for stable release (A is development/unstable). 04 is fourth minor version, i.e. fourth bugfix release in given major release. BEAM files and Erlang distribution protocol (ei) should always be compatible across two major version numbers. I.e. with current R14B04 instalation you should be able run .beam files compiled in R12 versions and R12 nodes should be able communicate with your new R14 nodes. API changes are much more conservative so you usually can be able compile and run source code from R7 ;-) Anyway experimental modules API can change even in minor version what happen in R13 with binary module if memory serves me right, but this really can happen only for experimental, unsupported or undocumented features.