implement main function for the program

app/Main.hs

@@ -1,6 +1,23 @@
 module Main (main) where
 
-import Lib
+import Ladder (ladderSolve, readDictionary)
+import System.Environment
+
+printHelpText :: String -> IO ()
+printHelpText msg = do
+  putStrLn (msg ++ "\n")
+  progName <- getProgName
+  putStrLn ("Usage: " ++ progName ++ " <filename> <start> <end>")
 
 main :: IO ()
-main = someFunc
+main = do
+  args <- getArgs
+  case args of
+    [dictFile, start, end] -> do
+      dict <- readDictionary dictFile
+      case ladderSolve dict start end of
+        Nothing -> putStrLn "No solution"
+        Just solution -> do
+          print solution
+          putStrLn ("Length: " ++ show (length solution))
+    _ -> printHelpText "Wrong arguments"

src/Ladder.hs

@@ -1,4 +1,4 @@
-module Ladder (readDictionary, mkLadderGraph) where
+module Ladder (readDictionary, ladderSolve) where
 
 import Data.Char (isLower)
 import qualified Data.List as L
@@ -8,6 +8,11 @@ import Prelude hiding (lines, words)
 
 type Dictionary = [String]
 
+ladderSolve :: Dictionary -> String -> String -> Maybe [String]
+ladderSolve dict start end =
+  let graph = mkLadderGraph dict
+   in G.bfsSearch graph start end
+
 readDictionary :: String -> IO Dictionary
 readDictionary filename = do
   text <- readFile filename
@@ -16,19 +21,19 @@ readDictionary filename = do
   return (L.nub lowercaseWords)
 
 mkLadderGraph :: Dictionary -> G.DiGraph String
-mkLadderGraph dict = G.buildDiGraph [(word, computeCandidates permMap word) | word <- dict]
+mkLadderGraph dict = G.buildDiGraph [(word, computeCandidates word) | word <- dict]
   where
     permMap = PM.createPermutationMap dict
 
-computeCandidates :: PM.PermutationMap -> String -> [String]
+    computeCandidates :: String -> [String]
-computeCandidates permMap word =
+    computeCandidates word =
-  -- Delete the original word from the permutations list
+      -- Delete the original word from the permutations list
-  L.delete word permutations
+      L.delete word permutations
-  where
+      where
-    removed = [L.delete c word | c <- word]
+        removed = [L.delete c word | c <- word]
-    added = [c : word | c <- ['a' .. 'z']]
+        added = [c : word | c <- ['a' .. 'z']]
-    modified = [x : L.delete y word | x <- ['a' .. 'z'], y <- word, x /= y]
+        modified = [x : L.delete y word | x <- ['a' .. 'z'], y <- word, x /= y]
-    -- Sort and deduplicate all the candidates
+        -- Sort and deduplicate all the candidates
-    candidates = L.nub $ map L.sort (added ++ removed ++ modified ++ [word])
+        candidates = L.nub $ map L.sort (added ++ removed ++ modified ++ [word])
-    -- For each candidate, lookup all its permutations
+        -- For each candidate, lookup all its permutations
-    permutations = L.concatMap (\w -> PM.findWithDefault [] w permMap) candidates
+        permutations = L.concatMap (\w -> PM.findWithDefault [] w permMap) candidates

src/Lib.hs

@@ -1,6 +0,0 @@
-module Lib
-    ( someFunc
-    ) where
-
-someFunc :: IO ()
-someFunc = putStrLn "someFunc"