add scheme evaluation

Anna.hs

@@ -5,6 +5,7 @@ import Data.Char (isSpace)
 import qualified Data.Text as T
 import System.IO
 import System.Directory
+import System.Process (readProcess)
 import Control.Monad
 import Control.Monad.IO.Class
 import qualified Network.Socket as N
@@ -74,6 +75,7 @@ tokenDispatch (Just username) (Just chn) ts = if elem "PRIVMSG" ts
               "!tz"       -> if "!tz" == last tokens
                              then timezone chn username
                              else timezone chn $ head $ tail tokens
+              "!eval"     -> evalScheme chn $ join $ intersperse " " $ tail tokens
               "!rollcall" -> rollcall chn
               "!anna"     -> anna chn
               _           -> return ()
@@ -131,6 +133,19 @@ timezone chn username = do
   else sendMessage chn $ username ++ " has not set their timezone. Use `echo '<timezone here>' > ~/.tz' to add your timezone."
     where sanitize = T.unpack . T.replace (T.pack "\n") T.empty . T.pack
 
+evalScheme :: String -> String -> Net ()
+evalScheme chn form = do
+  liftIO $ putStrLn form
+  result <- liftIO $ (\s -> s ++ "\n") <$> readProcess "guile" ["-c", expr] ""
+  sendMessage chn result
+    where expr = "(use-modules (ice-9 sandbox) \
+                  \            (rnrs exceptions)) \
+                  \ (display (guard (ex (else 'error)) \
+                  \   (eval-in-sandbox (read (open-input-string \"" ++ form ++ "\")) \
+                  \     #:bindings all-pure-and-impure-bindings)))"
+
+
+
 rollcall :: String -> Net ()
 rollcall chn = sendMessage chn "Hello! I respond to !anna, !qotd, and !greets. My source code is available at https://git.tilde.town/opfez/anna2"
 anna = rollcall