From 02b43330f265c4ed7d2aa75a695c235d627fc20e Mon Sep 17 00:00:00 2001
From: Alex Ozdemir <aozdemir@hmc.edu>
Date: Sat, 27 Jan 2018 17:40:10 -0500
Subject: [PATCH] Added metacommand `:list`

:list allows the user to get a list of all variables they have defined.
---
 src/Completion.hs  | 7 +------
 src/Environment.hs | 9 +++++++++
 src/Eval/Meta.hs   | 8 ++++++++
 src/Read.hs        | 3 ++-
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/Completion.hs b/src/Completion.hs
index b6be699..a35cc5c 100644
--- a/src/Completion.hs
+++ b/src/Completion.hs
@@ -17,14 +17,9 @@ complete =
 lookupCompletions :: String -> Env.Task [Completion]
 lookupCompletions string =
     do  env <- get
-        let defs = adjustDefs (Env.defs env)
+        let defs = Trie.unionL cmds $ Env.actualDefs env
         return (completions string defs)
     where
-      adjustDefs defs =
-          Trie.unionL cmds $
-          Trie.delete Env.firstVar $
-          Trie.delete Env.lastVar defs
-
       cmds =
           Trie.fromList
               [ (":exit", "")
diff --git a/src/Environment.hs b/src/Environment.hs
index 9ff3a62..cce8d09 100644
--- a/src/Environment.hs
+++ b/src/Environment.hs
@@ -44,6 +44,7 @@ data Config
     | Help (Maybe String)
     | Exit
     | Reset
+    | List
     deriving (Show, Eq)
 
 
@@ -66,6 +67,10 @@ needsPrint maybeDefName =
     Just _ ->
       False
 
+getName :: DefName -> String
+getName (DataDef s) = s
+getName (Import s) = s
+getName (VarDef s) = s
 
 
 -- ENVIRONMENT
@@ -82,6 +87,10 @@ data Env = Env
     deriving Show
 
 
+actualDefs :: Env -> Trie String
+actualDefs env = Trie.delete firstVar $
+          Trie.delete lastVar (defs env)
+
 empty :: FilePath -> FilePath -> Env
 empty compiler interpreter =
     Env compiler
diff --git a/src/Eval/Meta.hs b/src/Eval/Meta.hs
index 04c22b1..efff71c 100644
--- a/src/Eval/Meta.hs
+++ b/src/Eval/Meta.hs
@@ -4,9 +4,12 @@ module Eval.Meta (eval) where
 import Control.Monad.State (get, modify)
 import Control.Monad.Trans (liftIO)
 import qualified Data.List as List
+import Data.Maybe
+import qualified Data.Trie as Trie
 import System.Exit (ExitCode(ExitSuccess))
 
 import qualified Environment as Env
+import Read (extractDefName)
 
 
 eval :: Env.Config -> Env.Task (Maybe ExitCode)
@@ -19,6 +22,10 @@ eval config =
         do displayErr "Bad command\n" m
            display helpInfo
 
+    Env.List ->
+        do  env <- get
+            display $ unlines $ map Env.getName $ concatMap (maybeToList . extractDefName) $ Trie.elems $ Env.actualDefs env
+
     Env.InfoFlags m ->
         do displayErr "Bad flag\n" m
            display flagsInfo
@@ -89,4 +96,5 @@ helpInfo =
     \  :help\t\t\tList available commands\n\
     \  :flags\t\tManipulate flags sent to elm compiler\n\
     \  :reset\t\tClears all previous imports\n\
+    \  :list\t\t\tLists all defined variables\n\
     \  :exit\t\t\tExits elm-repl\n"
diff --git a/src/Read.hs b/src/Read.hs
index 442e883..63584a4 100644
--- a/src/Read.hs
+++ b/src/Read.hs
@@ -1,5 +1,5 @@
 {-# LANGUAGE OverloadedStrings #-}
-module Read (input) where
+module Read (input, extractDefName) where
 
 import qualified Data.Char as Char
 import qualified Data.List as List
@@ -52,6 +52,7 @@ config =
       case flag of
         "exit"  -> ok Env.Exit
         "reset" -> ok Env.Reset
+        "list"  -> ok Env.List
         "help"  -> ok (Env.Help Nothing)
         "flags" -> ok (Env.InfoFlags Nothing) <|> flags
         _       -> return $ Env.Help (Just flag)