Haskell: steps 4-6. Line editing. Simpler fn calls.

1 files changed, 30 insertions, 0 deletions

diff --git a/haskell/Readline.hs b/haskell/Readline.hs
new file mode 100644
index 0000000..483c827
--- /dev/null
+++ b/haskell/Readline.hs
@@ -0,0 +1,30 @@
+module Readline
+( readline, load_history )
+where
+
+-- Pick one of these:
+-- GPL license
+import qualified System.Console.Readline as RL
+-- BSD license
+--import qualified System.Console.Editline.Readline as RL
+
+import System.Directory (getHomeDirectory)
+
+history_file = do
+    home <- getHomeDirectory
+    return $ home ++ "/.mal-history"
+
+load_history = do
+    hfile <- history_file
+    content <- readFile hfile
+    mapM RL.addHistory (lines content)
+
+readline prompt = do
+    hfile <- history_file
+    maybeLine <- RL.readline prompt
+    case maybeLine of 
+         Just line -> do
+             appendFile hfile (line ++ "\n")
+             RL.addHistory line
+             return maybeLine
+         _ -> return maybeLine