Capabilities can contain +

[cocreature]

At least the LITERAL+ capabilty contains a + and that breaks your parsing, since you only accept things matching isAtomChar and + is not among those.

I am not sure if it makes sense to modify isAtomChar or add a special case for the parsing of capabilities.

[mkawalec]

This was an error in the way I was handling atom characters (too few were accepted). Should be fixed now, latest updated version pushed to Hackage.

[cocreature]

Thanks, it’s fixed