Haskell module names have to satisfy the Haskell (including the hierarchical module namespace extension) lexical syntax:

modid -> [modid.] large {small | large | digit | ' }

encodeModuleName is an injective function into the set of module names defined by modid. The function often preserves names. The function always preserves .s.

Precondition: The input must not start or end with ., and no two .s may be adjacent.