'''Ticket:''' #20

== Eliminate . as an operator ==

In early Haskell, . was used as function composition. In later versions of Haskell, it also became used as a name qualifier. 

These two uses do not fit well together, leading to special lexical rules (P11 of the report). As a test, before reading the report, can you lex the following: "f.g", "F.g", "F . g", "f..", "F..", and "F.". I couldn't.
(See QualifiedIdentifiers for a related problem.)

Proposed syntaxes for [wiki:RankNTypes] and ExistentialQuantification also use . as a special symbol.

== Proposal ==

 * Add {{{.}}} to ''reservedop'' in the lexical syntax
 * move qualified identifiers ({{{qvarid}}}, {{{qconid}}} etc.) from the lexical syntax to the context-free syntax

(Note: {{{.}}} also appears in the syntax as a decimal point in floats).

== Pros ==

 * Much much simpler. Not impossible to remember.
 * Paves the way for using {{{.}}} as the selection operator in improved record or module systems

== Cons ==

 * We lose . as composition. Mostly this doesn't matter as $ is probably more common in reality anyway (a highly controversial view, unsupported by evidence!). Perhaps use
   {{{`o`}}} as infix composition instead if it is really important.  Note that {{{`o`}}} is three characters - it
   would be nicer to use plain {{{o}}} infix, but that would require another special lexical rule.  Others alternatives
   for composition include [wiki:Unicode] symbols such as centred-dot ·, a bullet point •, an unfilled bullet point, the ring operator (U+2218), the
   degree sign °, the masculine ordinal indicator º, stroked circle ø, and so on.  All of these resemble the mathematical
   symbol, and some of them are available in the Latin-1 subset.

 * Breaks quite a lot of code