diff --git a/prefix-expression.cabal b/prefix-expression.cabal
--- a/prefix-expression.cabal
+++ b/prefix-expression.cabal
@@ -1,13 +1,13 @@
 name:                prefix-expression
-version:             1.0.0
+version:             1.0.1
 -- synopsis:
 description:         convert infix to prefix expression
-homepage:            https://github.com/VonFry/ParseExpression#readme
+homepage:            https://github.com/VonFry/prefix-expression
 license:             GPL-3
 license-file:        LICENSE
 author:              Vonfry
 maintainer:          vonfry314@gmail.com
-copyright:           Copyright: ©  2017 Vonfry
+copyright:           Copyright: ©  2018 Vonfry
 category:            Text
 build-type:          Simple
 cabal-version:       >=1.10
diff --git a/src/Text/Exp/Prefix.hs b/src/Text/Exp/Prefix.hs
--- a/src/Text/Exp/Prefix.hs
+++ b/src/Text/Exp/Prefix.hs
@@ -1,4 +1,4 @@
--- | Convert infix exp to prefix exp. The expression's operators contains: @ + - * / \ ** || && ! =~ ( ) @
+-- | Convert infix exp to prefix exp. The expression's operators contains: @ + - * / \ ^ || && ! =~ ( ) @
 module Text.Exp.Prefix (
     fromInfix
   ) where
@@ -9,7 +9,7 @@
 
 -- ^ a operators list which cantains a list in order with precedence.
 expOperators :: [[(String, Int)]]
-expOperators   = [[("**", 2)], [("*", 2), ("/", 2), ("\\", 2)], [("+", 2), ("-", 2)], [("=~", 2)], [("&&", 2)], [("||", 2)], [("!", 1)], [("(", 0), (")", 0)]]
+expOperators   = [[("^", 2)], [("*", 2), ("/", 2), ("\\", 2)], [("+", 2), ("-", 2)], [("=~", 2)], [("&&", 2)], [("||", 2)], [("!", 1)], [("(", 0), (")", 0)]]
 expOperators'  = foldr (++) [] expOperators
 expOperators'' = unzip expOperators'
 
@@ -60,7 +60,7 @@
             = (opStack'', popedStack)
 
 checkInfixExp :: String -> Bool
-checkInfixExp exp = exp =~ "((&&|\\*\\*|\\|\\||=~|\\(|\\)|\\+|-|\\*|/|\\\\) *(&&|\\*\\*|\\|\\||=~|\\(|\\)|\\+|-|\\*|/|\\\\))|([0-z]+ +[0-z]+)"
+checkInfixExp exp = not $ exp =~ "((&&|\\|\\||\\^|=~|\\+|-|\\*|/|\\\\) *(&&|\\|\\||\\^|=~|\\+|-|\\*|/|\\\\))|([0-9A-Za-z]+ +[0-9A-Za-z]+)"
 
 checkOpArgs :: [String] -> Bool
 checkOpArgs stack = checkOpArgs' stack "" 0 0 0 == length stack
@@ -113,12 +113,12 @@
     splitExp' sp exp
       | "" <- exp = filter (\x -> x /= "") sp
       | otherwise
-      = let match = exp =~ " +|\\( *[\\+-][0-z]+ *\\)|&&|\\*\\*|\\|\\||=~|!|\\(|\\)|\\+|-|\\*|/|\\\\" :: String
+      = let match = exp =~ " +|\\( *[\\+-][0-9A-Za-z]+ *\\)|&&|\\^|\\|\\||=~|!|\\(|\\)|\\+|-|\\*|/|\\\\" :: String
         in if match /= ""
            then let Just (idx, _) = elemSubIndex match exp
                     (arg, exp')   = splitAt idx exp
                     (op, exp'')   = splitAt (length match) exp'
-                    op' = if op =~ "\\( *[\\+-][0-z]+ *\\)" :: Bool
+                    op' = if op =~ "\\( *[\\+-][0-9A-Za-z]+ *\\)" :: Bool
                              then filter (not.(`elem`"()")) op
                              else op
                  in splitExp' (sp ++ [filter (not.isSpace) arg, filter (not.isSpace) op']) exp''
@@ -126,7 +126,7 @@
 
 doPrefixNegative :: String -> String
 doPrefixNegative exp =
-    let match = exp =~ "^ *[\\+-][0-z]+" :: String
+    let match = exp =~ "^ *[\\+-][0-9A-Za-z]+" :: String
     in if match /= ""
         then let Just (t, d) = elemSubIndex match exp
             in take t exp ++ "(" ++ match ++ ")" ++ drop d exp
diff --git a/test/Text/Exp/PrefixSpec.hs b/test/Text/Exp/PrefixSpec.hs
--- a/test/Text/Exp/PrefixSpec.hs
+++ b/test/Text/Exp/PrefixSpec.hs
@@ -12,10 +12,11 @@
 spec = do
   describe "from infix" $ do
     it "correct" $ do
-      fromInfix "!((1 + 3) * 3 - 4 ** 5)" `shouldBe` Right "! - * + 1 3 3 ** 4 5"
+      fromInfix "!((1 + 3) * 3 - 4 ^ 5)" `shouldBe` Right "! - * + 1 3 3 ^ 4 5"
       fromInfix "+2 * (-1) + 3" `shouldBe` Right "+ * +2 -1 3"
+      fromInfix "a + b + c" `shouldBe` Right "+ + a b c"
     it "failed" $ do
-      (isLeft $ fromInfix "!((1 + 3) * 3 - 4 ** 5") `shouldBe` True
+      (isLeft $ fromInfix "!((1 + 3) * 3 - 4 ^ 5") `shouldBe` True
       (isLeft $ fromInfix "1 + + 2") `shouldBe` True
       (isLeft $ fromInfix "(1 +) + 2") `shouldBe` True
   where