loadConcr, unloadConcr and addLiteral modify the Concr structure as a side
effect. This means that other functions with a Concr argument (e.g. parse
and linearize) are no longer pure.
Possible solutions:
1. Don't try to hide the imperative nature of the C run-time system: remove
all uses of unsafePerformIO and let all functions operate in the IO monad.
2. Don't export functions with side effects. Perhaps the desired functionality
of loadConcr, unloadConcr and addLiteral can be folded into readPGF.
The Concr structures can then treaded as immutable after after the
readPGF function returns...
PGF exports the public, stable API.
PGF.Internal exports additional things needed in the GF compiler & shell,
including the nonstardard version of Data.Binary.
From the documentation: the throwIO variant should be used in preference to
throw to raise an exception within the IO monad because it guarantees ordering
with respect to other IO operations, whereas throw does not.
Also removed some unused imports.
1. Like pgf-translate, it now shows one result at a time, press Enter to get
more results.
2. You can load a new grammar with the command 'i <path-to-pgf>'
If the C run-time library is compiled and installed on your system, you can now
do 'cabal configure -fc-runtime' to get the following extras:
+ The haskell binding to the C run-time library will be included in the
PGF library (so you can import it in Haskell applications).
Documentation on the new modules will be included when you run
'cabal haddock'.
+ The new command 'pgf-shell', implemented on top of haskell binding to
the C run-time system.
+ Three new commands in the web API: c-parse, c-linearize and
c-translate. Their interfaces are similar to the corresponding commands
without the "c-" prefix, but they should be considered preliminary.
* The haskell-bind.cabal file makes it easy to build the haskell binding and
use it in ghci.
* pgf-shell.hs is a simple example of how to use the haskell binding.
Change the type of getConcr from
getConcr :: PGF -> Language -> Concr
to
getConcr :: PGF -> Language -> Maybe Concr
This is to prevent programs from crashing later if you try to select a
concrete syntax that is not present in a grammar.
