Generate the bit in the user guide where we say what -fglasgow-exts does

Stops the docs going out of sync with the code.

1 files changed, 39 insertions, 0 deletions

diff --git a/utils/mkUserGuidePart/Main.hs b/utils/mkUserGuidePart/Main.hs
new file mode 100644
index 0000000000..114114ca1c
--- /dev/null
+++ b/utils/mkUserGuidePart/Main.hs
@@ -0,0 +1,39 @@
+
+module Main (main) where
+
+import DynFlags
+
+import Data.List
+import System.Environment
+
+main :: IO ()
+main = do args <- getArgs
+          case args of
+              [] -> error "Need to give filename to generate as an argument"
+              [f] ->
+                  case f of
+                      "docs/users_guide/what_glasgow_exts_does.gen.xml" ->
+                          writeFile f whatGlasgowExtsDoes
+                      _ ->
+                          error ("Don't know what to do for " ++ show f)
+              _ -> error "Bad args"
+
+whatGlasgowExtsDoes :: String
+whatGlasgowExtsDoes = case maybeInitLast glasgowExtsFlags of
+                      Just (xs, x) ->
+                          let xs' = map mkInitLine xs
+                              x' = mkLastLine x
+                          in unlines (xs' ++ [x'])
+                      Nothing ->
+                          error "glasgowExtsFlags is empty?"
+    where mkInitLine = mkLine ','
+          mkLastLine = mkLine '.'
+          mkLine c f = case stripPrefix "Opt_" (show f) of
+                       Just ext -> "<option>-X" ++ ext ++ "</option>" ++ [c]
+                       Nothing -> error ("Can't parse extension: " ++ show f)
+
+maybeInitLast :: [a] -> Maybe ([a], a)
+maybeInitLast xs = case reverse xs of
+                   (y : ys) -> Just (reverse ys, y)
+                   _        -> Nothing
+