Eliminate mutual dependencies between the GF compiler and the PGF library

+ References to modules under src/compiler have been eliminated from the PGF
  library (under src/runtime/haskell). Only two functions had to be moved (from
  GF.Data.Utilities to PGF.Utilities) to make this possible, other apparent
  dependencies turned out to be vacuous.

+ In gf.cabal, the GF executable no longer directly depends on the PGF library
  source directory, but only on the exposed library modules. This means that
  there is less duplication in gf.cabal and that the 30 modules in the
  PGF library will no longer be compiled twice while building GF.

  To make this possible, additional PGF library modules have been exposed, even
  though they should probably be considered for internal use only. They could
  be collected in a PGF.Internal module, or marked as "unstable", to make
  this explicit.

+ Also, by using the -fwarn-unused-imports flag, ~220 redundant imports were
  found and removed, reducing the total number of imports by ~15%.

5 files changed, 11 insertions, 16 deletions

diff --git a/src/compiler/GF/Command/Abstract.hs b/src/compiler/GF/Command/Abstract.hs
index 5469f12ac..8b7b824f0 100644
--- a/src/compiler/GF/Command/Abstract.hs
+++ b/src/compiler/GF/Command/Abstract.hs
@@ -1,7 +1,6 @@
 module GF.Command.Abstract where
 
-import PGF.CId(CId,mkCId)
-import PGF.Data(Expr)
+import PGF(CId,mkCId,Expr)
 
 type Ident = String
 
diff --git a/src/compiler/GF/Command/Commands.hs b/src/compiler/GF/Command/Commands.hs
index 8a19d2729..a05b3cf20 100644
--- a/src/compiler/GF/Command/Commands.hs
+++ b/src/compiler/GF/Command/Commands.hs
@@ -14,13 +14,12 @@ import Prelude hiding (putStrLn)
 
 import PGF
 
-import PGF.VisualizeTree(getDepLabels)
 import PGF.Macros(lookStartCat,functionsToCat,lookValCat,restrictPGF,hasLin)
 import PGF.Data(abstract,funs,cats,Literal(LStr),Expr(EFun,ELit)) ----
-import PGF.Morphology(isInMorpho,morphoKnown)
+--import PGF.Morphology(isInMorpho,morphoKnown)
 import PGF.Printer(ppFun,ppCat)
-import PGF.Probabilistic(rankTreesByProbs,probTree,setProbabilities)
-import PGF.Generate (generateRandomFrom) ----
+--import PGF.Probabilistic(rankTreesByProbs,probTree,setProbabilities)
+--import PGF.Generate (generateRandomFrom) ----
 import PGF.Tree (Tree(Fun), expr2tree, tree2expr)
 import PGF.Optimize(optimizePGF)
 
@@ -30,7 +29,7 @@ import GF.Compile.ExampleBased
 import GF.Infra.Option (noOptions, readOutputFormat, outputFormatsExpl)
 import GF.Infra.UseIO(writeUTF8File)
 import GF.Infra.SIO
-import GF.Data.ErrM ----
+--import GF.Data.ErrM ----
 import GF.Command.Abstract
 import GF.Command.Messages
 import GF.Text.Lexing
@@ -43,13 +42,13 @@ import GF.Command.TreeOperations ---- temporary place for typecheck and compute
 import GF.Data.Operations
 
 import Data.Binary (encodeFile)
-import Data.List
+import Data.List(intersperse,nub)
 import Data.Maybe
 import qualified Data.Map as Map
 --import System.Cmd(system) -- use GF.Infra.UseIO.restricedSystem instead!
 import Text.PrettyPrint
 import Data.List (sort)
-import Debug.Trace
+--import Debug.Trace
 --import System.Random (newStdGen) ----
 
 
@@ -940,7 +939,7 @@ allCommands = Map.fromList [
          let outp = valStrOpts "output" "dot" opts
          mlab <- case file of
            "" -> return Nothing
-           _  -> restricted (readFile file) >>= return . Just . getDepLabels . lines
+           _  -> (Just . getDepLabels . lines) `fmap` restricted (readFile file)
          let lang = optLang pgf opts
          let grphs = unlines $ map (graphvizDependencyTree outp debug mlab Nothing pgf lang) es
          if isFlag "view" opts || isFlag "format" opts then do
diff --git a/src/compiler/GF/Command/Importing.hs b/src/compiler/GF/Command/Importing.hs
index ce06156e4..4697e8b64 100644
--- a/src/compiler/GF/Command/Importing.hs
+++ b/src/compiler/GF/Command/Importing.hs
@@ -12,7 +12,7 @@ import GF.Infra.UseIO
 import GF.Infra.Option
 import GF.Data.ErrM
 
-import Data.List (nubBy)
+--import Data.List (nubBy)
 import System.FilePath
 
 -- import a grammar in an environment where it extends an existing grammar
diff --git a/src/compiler/GF/Command/Interpreter.hs b/src/compiler/GF/Command/Interpreter.hs
index 78f243fff..f27ba47da 100644
--- a/src/compiler/GF/Command/Interpreter.hs
+++ b/src/compiler/GF/Command/Interpreter.hs
@@ -13,10 +13,8 @@ import GF.Command.Abstract
 import GF.Command.Parse
 import PGF
 import PGF.Data
-import PGF.Morphology
-import GF.System.Signal
+--import PGF.Morphology
 import GF.Infra.SIO
-import GF.Infra.Option
 
 import Text.PrettyPrint
 import Control.Monad(when)
diff --git a/src/compiler/GF/Command/Parse.hs b/src/compiler/GF/Command/Parse.hs
index d68a0bcd7..855fdb54e 100644
--- a/src/compiler/GF/Command/Parse.hs
+++ b/src/compiler/GF/Command/Parse.hs
@@ -1,7 +1,6 @@
 module GF.Command.Parse(readCommandLine, pCommand) where
 
-import PGF.CId
-import PGF.Expr
+import PGF
 import GF.Command.Abstract
 
 import Data.Char