For further separation of pretty printing concerns from conversion concerns,
the Haskell AST and pretty printer has been moved to its own module,
GF.Haskell, also allowing it to be reused in other places where Haskell
code is generated.
+ 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.
+ Instead of including lists of parameter values generated by GF, generate
code to enumerate parameter values (in the same order as GF). This seems
to give a factor of 2-3 code size reduction in the Phrasebook (e.g.
from 84MB to 25MB for Hin, from 338MB to 154MB for Fre).
+ Deduplicate table entries, i.e. convert "table [..,E,..,E,..,E,..]" into
"let x = E in table [..,x,..,x,..,x,..]". This gives even more significant
code size reduction in some cases, e.g. from 569MB to 15MB for
PhrasebookFin.
All phrasebook languages can now be converted to compilable Haskell code,
except PhrasebookPes, which still has the name clash problem.
Many Phrasebook languages can now be converted to compilable Haskell code.
Some languages (Fre, Hin, Snd, Urd) generate too much Haskell code to be
practically useful (e.g. 338MB for Fre). One language (Fin) took too long
to convert to Haskell. One language (Pes) has problems with name clashes in
the generated Haskell code.
STILL TODO:
- variants
- pre { ... }
- reduce code duplication for large tables
- generate qualified names to avoid name clashes
The translation is currently good enough to translate all concrete syntaxes
of the Foods and Letter grammars, and some concrete syntaxes of the Phrasebook
grammar (e.g. PhrasebookEng & PhrasebookSpa works, but there are problems with
e.g. PhrasebookSwe and PhrasebookChi)
This functionality is enabled by running
gf -make -output-format=haskell -haskell=concrete ...
TODO:
- variants
- pre { ... }
- eta expansion of linearization functions
- record subtyping can still cause type errors in the Haskell code
in some cases
- reduce code large tables
