+ Some additional simplifying rewrites.
+ Use an intermediate representation for Haskell types, for separation of
concerns and cleaner code.
+ Pretty printer layout tuning
+ Code cleanup.
Introduced an intermediate representation for the generated Haskell expressions.
This allows pretty printing concerns to be separated from conversion concerns,
and makes it easy to apply some simplifying rewrites to the generated
expressions, e.g.
[x] ++ [y] ==> [x,y]
pure f <*> x ==> f <$> x
f <$> pure x ==> pure (f x)
join (pure x) ==> x
By adding the flag -haskell=variants to the command line, GF will now generate
linearization functions in Haskell that support variants. Variants are
represented as lists in Haskell.
Variants inside pre { ... } expressions are still ignored.
TODO: apply some monad laws to generate more compact code (using an
intermediate representation of the generated Haskell code, instead of
pretty printing directly from the GF code).
Move the Haskell representation of the common linearization type {s:T} to the
shared module PGF.Haskell, so that the same overloaded projection function
proj_s can be used for all concrete syntaxes.
Common code has been lifted out from the generated Haskell modules to
an auxiliary module PGF.Haskell, which is currently included in the
regular PGF library, although it is independent of it and probably belongs
in a separate library.
The type Str used by linearization functions is now based on a token
type Tok, which is defined in PGF.Haskell.
PGF.Haskell.Tok is similar to the type GF.Data.Str.Tok, but it has
constructors for the special tokens BIND, SOFT_BIND and CAPIT, and there is
a function
fromStr :: Str -> String
that computes the effects of these special tokens.
