part1 excercises

exercises/Set1.hs

@@ -20,14 +20,16 @@ import Mooc.Todo
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 -- Ex 1: define variables one and two. They should have type Int and
 -- values 1 and 2, respectively.
-
+one, two :: Int
+one = 1
+two = 2
 
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 -- Ex 2: define the function double of type Integer->Integer. Double
 -- should take one argument and return it multiplied by two.
 
 double :: Integer -> Integer
-double x = todo
+double x = x * 2
 
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 -- Ex 3: define the function quadruple that uses the function double
@@ -35,7 +37,7 @@ double x = todo
 -- four.
 
 quadruple :: Integer -> Integer
-quadruple x = todo
+quadruple x = double (double x)
 
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 -- Ex 4: define the function distance. It should take four arguments of
@@ -50,8 +52,8 @@ quadruple x = todo
 -- Examples:
 --   distance 0 0 1 1  ==>  1.4142135...
 --   distance 1 1 4 5  ==>  5.0
-
-distance = todo
+distance :: Double -> Double -> Double -> Double -> Double
+distance x1 y1 x2 y2 = sqrt ((x2-x1)^2 + (y2-y1)^2)
 
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 -- Ex 5: define the function eeny that returns "eeny" for even inputs
@@ -60,7 +62,9 @@ distance = todo
 -- Ps. have a look at the built in function "even"
 
 eeny :: Integer -> String
-eeny = todo
+eeny num = if num `mod` 2 == 0
+            then "eeny"
+            else "meeny"
 
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 -- Ex 6: here's the function checkPassword from the course material.
@@ -68,7 +72,7 @@ eeny = todo
 -- "mellon".
 
 checkPassword :: String -> String
-checkPassword password = if password == "swordfish"
+checkPassword password = if password == "swordfish" || password == "mellon"
                          then "You're in."
                          else "ACCESS DENIED!"
 
@@ -82,7 +86,11 @@ checkPassword password = if password == "swordfish"
 -- in grams, and returns the cost in credits.
 
 postagePrice :: Int -> Int
-postagePrice = todo
+postagePrice grams = if grams <= 500
+                        then 250
+                        else if grams > 500 && grams <= 5000
+                            then 300 + grams
+                        else 6000
 
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 -- Ex 8: define a function isZero that returns True if it is given an
@@ -92,7 +100,9 @@ postagePrice = todo
 --
 -- Ps. remember, the type of booleans in haskell is Bool
 
-isZero = todo
+isZero :: Integer -> Bool
+isZero 0 = True
+isZero _ = False
 
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 -- Ex 9: implement using recursion a function sumTo such that
@@ -100,14 +110,16 @@ isZero = todo
 -- computes the sum 1+2+...+n
 
 sumTo :: Integer -> Integer
-sumTo = todo
+sumTo 1 = 1
+sumTo n = n + sumTo (n-1)
 
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 -- Ex 10: power n k should compute n to the power k (i.e. n^k)
 -- Use recursion.
 
 power :: Integer -> Integer -> Integer
-power = todo
+power n 1 = n
+power n k = n * power n (k-1)
 
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 -- Ex 11: ilog3 n should be the number of times you can divide given
@@ -126,4 +138,7 @@ power = todo
 --   ilog3 7 ==> 2
 
 ilog3 :: Integer -> Integer
-ilog3 = todo
+ilog3 0 = 1
+ilog3 1 = 1
+ilog3 2 = 1
+ilog3 n = ilog3 (n `div` 3) + 1