Haskell/99Questions/93_EvalPuzzle: Add

Author: GHScan

Haskell/99Questions/93_EvalPuzzle/main.hs

@@ -1,47 +1,32 @@
 import Data.List
 
 main = print output
-output = genEqual [2,3,5,7,11]
+output = puzzle [2,3,5,7,11]
 
-data ExpNode = Const Float | BinOp Char ExpNode ExpNode deriving (Show)
+data ExpNode = Const Float | BinExp Char ExpNode ExpNode deriving (Show)
 
 ops = "+-*/"
 getOpPrior '+' = 1
 getOpPrior '-' = 1
 getOpPrior '*' = 5
 getOpPrior '/' = 5
 
-reduceNodesList nodesL
-    | all ((==1).length) nodesL = nodesL
-reduceNodesList nodesL = reduceNodesList$ concatMap reduceNodes nodesL
-    where
-    reduceNodes nodes@[n] = [nodes]
-    reduceNodes nodes = concatMap buildAt [0..length nodes - 2]
-        where 
-        buildAt i = [left++BinOp op h1 h2:right|op<-ops]
-            where
-            (left,h1:h2:right) = splitAt i nodes
-        
-buildTreeList l = map head $ reduceNodesList [map Const l] 
-
-getTreeVal (Const i) = i
-getTreeVal (BinOp op l r)
-    | op == '+' = lv + rv
-    | op == '-' = lv - rv
-    | op == '*' = lv * rv
-    | op == '/' && rv == 0 = lv / 0.000001
-    | op == '/' = lv / rv
-    where (lv,rv) = (getTreeVal l, getTreeVal r)
-
-getTreeStr pPrior (Const i) = show $ floor i
-getTreeStr pPrior (BinOp op l r) = if curProir<pPrior then '(':raws++")" else raws
-    where
-    curProir = getOpPrior op
-    raws = getTreeStr curProir l ++ [op] ++ getTreeStr (curProir+1) r
+evalByOp '+' l r = l + r
+evalByOp '-' l r = l - r
+evalByOp '*' l r = l * r
+evalByOp '/' l r 
+    | r == 0 = l / 0.00001
+    | otherwise = l / r
 
-genEqual l = concatMap genAt [1..length l - 1]
+getNodeStr pPrior (Const f) = show $ floor f
+getNodeStr pPrior (BinExp op l r) = if curPrior<pPrior then '(':str++")" else str
     where
-    genAt i = [getTreeStr 0 lt++'=':getTreeStr 0 rt|(lt,lv)<-toValTreeList left,(rt,rv)<-toValTreeList right,lv==rv]
-        where
-        (left,right) = splitAt i l
-        toValTreeList l = map (\t->(t,getTreeVal t)) $ buildTreeList l
+    curPrior = getOpPrior op
+    str = getNodeStr curPrior l ++ op: getNodeStr (curPrior + 1) r
+
+splits l = init$ tail$ zip (inits l) (tails l)
+
+toExpList [x] = [(x, Const x)]
+toExpList l = [(evalByOp op lv rv,BinExp op lt rt)|(left, right)<-splits l,(lv,lt)<-toExpList left,(rv,rt)<-toExpList right,op<-ops]
+
+puzzle l = [getNodeStr 0 lt ++ '=':getNodeStr 0 rt|(left,right)<-splits l,(lv,lt)<-toExpList left,(rv,rt)<-toExpList right,lv==rv]