Support a more complete (and simple) requirements gathering mechanism,

and add support for binary operations.

This version of requirements generation simply generates every numeric
size within a provided range, and then will reject trait implementations
that rely on values outside this range. It should be a little more easy
to reason about, and easier to make local changes as I (inevitably) need
to modify rules.

generation/src/File.hs

@@ -0,0 +1,66 @@
+module File(
+         File(..),
+         Task(..),
+         addModuleTasks,
+         makeTask
+       )
+ where
+
+import Control.Monad(forM_)
+import Data.Char(toUpper)
+import qualified Data.Map.Strict as Map
+import Gen(Gen,blank,out)
+import System.FilePath(takeBaseName,takeDirectory,takeFileName,(</>))
+
+data File = File {
+    predicate :: Word -> [Word] -> Bool,
+    outputName :: FilePath,
+    generator :: Word -> Gen ()
+}
+
+data Task = Task {
+    outputFile :: FilePath,
+    fileGenerator :: Gen ()
+}
+
+makeTask :: FilePath ->
+            Word -> [Word] ->
+            File ->
+            Maybe Task
+makeTask base size allSizes file
+  | predicate file size allSizes =
+     Just Task {
+         outputFile = base </> ("u" ++ show size) </> outputName file <> ".rs",
+         fileGenerator = generator file size
+     }
+  | otherwise =
+     Nothing
+
+addModuleTasks :: FilePath -> [Task] -> [Task]
+addModuleTasks base baseTasks = unsignedTask : (baseTasks ++ moduleTasks)
+ where
+  moduleMap = foldr addModuleInfo Map.empty baseTasks
+  addModuleInfo task =
+    Map.insertWith (++) (takeDirectory (outputFile task))
+                        [takeBaseName (outputFile task)]
+  moduleTasks = Map.foldrWithKey generateModuleTask [] moduleMap
+  generateModuleTask directory mods acc = acc ++ [Task {
+      outputFile = directory </> "mod.rs",
+      fileGenerator =
+        do forM_ mods $ \ modle -> out ("mod " ++ modle ++ ";")
+           blank
+           out ("pub use base::" ++ upcase (takeFileName directory) ++ ";")
+  }]
+  unsignedTask = Task {
+      outputFile = base </> "unsigned" </> "mod.rs",
+      fileGenerator =
+        do forM_ (Map.keys moduleMap) $ \ key ->
+             out ("mod " ++ takeFileName key ++ ";")
+           blank
+           forM_ (Map.keys moduleMap) $ \ key ->
+             out ("pub use " ++ takeFileName key ++ "::" ++
+                  upcase (takeFileName key) ++ ";")
+  }
+ 
+upcase :: String -> String
+upcase = map toUpper