Add sum-of-multiples example

Author: koladilip

sum-of-multiples/README.md

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+# Sum Of Multiples
+
+Given a number, find the sum of all the unique multiples of particular numbers up to
+but not including that number.
+
+If we list all the natural numbers below 20 that are multiples of 3 or 5,
+we get 3, 5, 6, 9, 10, 12, 15, and 18.
+
+The sum of these multiples is 78.
+
+
+## Getting Started
+
+Please refer to the [installation](https://exercism.io/tracks/haskell/installation)
+and [learning](https://exercism.io/tracks/haskell/learning) help pages.
+
+## Running the tests
+
+To run the test suite, execute the following command:
+
+```bash
+stack test
+```
+
+#### If you get an error message like this...
+
+```
+No .cabal file found in directory
+```
+
+You are probably running an old stack version and need
+to upgrade it.
+
+#### Otherwise, if you get an error message like this...
+
+```
+No compiler found, expected minor version match with...
+Try running "stack setup" to install the correct GHC...
+```
+
+Just do as it says and it will download and install
+the correct compiler version:
+
+```bash
+stack setup
+```
+
+## Running *GHCi*
+
+If you want to play with your solution in GHCi, just run the command:
+
+```bash
+stack ghci
+```
+
+## Feedback, Issues, Pull Requests
+
+The [exercism/haskell](https://github.com/exercism/haskell) repository on
+GitHub is the home for all of the Haskell exercises.
+
+If you have feedback about an exercise, or want to help implementing a new
+one, head over there and create an issue.  We'll do our best to help you!
+
+## Source
+
+A variation on Problem 1 at Project Euler [http://projecteuler.net/problem=1](http://projecteuler.net/problem=1)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

sum-of-multiples/package.yaml

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+name: sum-of-multiples
+version: 1.5.0.10
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: SumOfMultiples
+  source-dirs: src
+  ghc-options: -Wall
+  # dependencies:
+  # - foo       # List here the packages you
+  # - bar       # want to use in your solution.
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - sum-of-multiples
+      - hspec

sum-of-multiples/src/SumOfMultiples.hs

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+module SumOfMultiples (sumOfMultiples) where
+
+sumOfMultiples :: [Integer] -> Integer -> Integer
+sumOfMultiples factors limit = multiples (limit-1) 
+    where 
+        factors' = [f | f <- factors, f>0]
+        anyFactors n  = any (\f -> (rem n f) == 0) factors'
+        multiples l
+            | l>0 && anyFactors l = l + multiples (l-1)
+            | l>0 = multiples (l-1)
+            | otherwise = 0
+

sum-of-multiples/stack.yaml

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+resolver: lts-15.8

sum-of-multiples/stack.yaml.lock

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+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages: []
+snapshots:
+- completed:
+    size: 492015
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/15/8.yaml
+    sha256: 926bc3d70249dd0ba05277ff00943c0addb35b627cb641752669e7cf771310d0
+  original: lts-15.8

sum-of-multiples/sum-of-multiples.cabal

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+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.33.0.
+--
+-- see: https://github.com/sol/hpack
+--
+-- hash: af1be49874642abc6b07ca1898722e7c6220dbf1d18092102a163446f2b7490d
+
+name:           sum-of-multiples
+version:        1.5.0.10
+build-type:     Simple
+
+library
+  exposed-modules:
+      SumOfMultiples
+  other-modules:
+      Paths_sum_of_multiples
+  hs-source-dirs:
+      src
+  ghc-options: -Wall
+  build-depends:
+      base
+  default-language: Haskell2010
+
+test-suite test
+  type: exitcode-stdio-1.0
+  main-is: Tests.hs
+  other-modules:
+      Paths_sum_of_multiples
+  hs-source-dirs:
+      test
+  build-depends:
+      base
+    , hspec
+    , sum-of-multiples
+  default-language: Haskell2010

sum-of-multiples/test/Tests.hs

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+{-# OPTIONS_GHC -fno-warn-type-defaults #-}
+{-# LANGUAGE RecordWildCards #-}
+
+import Data.Foldable     (for_)
+import Test.Hspec        (Spec, describe, it, shouldBe)
+import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)
+
+import SumOfMultiples (sumOfMultiples)
+
+main :: IO ()
+main = hspecWith defaultConfig {configFastFail = True} specs
+
+specs :: Spec
+specs = describe "sumOfMultiples" $ for_ cases test
+  where
+    test Case{..} = it description' assertion
+      where
+        description' = unwords [show factors, show limit, "--", description]
+        assertion   = expression `shouldBe` fromIntegral expected
+        expression  = sumOfMultiples (fromIntegral <$> factors)
+                                     (fromIntegral     limit  )
+
+data Case = Case { factors     :: [Integer]
+                 , limit       ::  Integer
+                 , expected    ::  Integer
+                 , description ::  String
+                 }
+
+cases :: [Case]
+cases = [ Case { factors  = [3, 5]
+               , limit    = 1
+               , expected = 0
+               , description = "no multiples within limit"
+               }
+        , Case { factors  = [3, 5]
+               , limit    = 4
+               , expected = 3
+               , description = "one factor has multiples within limit"
+               }
+        , Case { factors  = [3]
+               , limit    = 7
+               , expected = 9
+               , description = "more than one multiple within limit"
+               }
+        , Case { factors  = [3, 5]
+               , limit    = 10
+               , expected = 23
+               , description = "more than one factor with multiples within limit"
+               }
+        , Case { factors  = [3, 5]
+               , limit    = 100
+               , expected = 2318
+               , description = "each multiple is only counted once"
+               }
+        , Case { factors  = [3, 5]
+               , limit    = 1000
+               , expected = 233168
+               , description = "a much larger limit"
+               }
+        , Case { factors  = [7, 13, 17]
+               , limit    = 20
+               , expected = 51
+               , description = "three factors"
+               }
+        , Case { factors  = [4, 6]
+               , limit    = 15
+               , expected = 30
+               , description = "factors not relatively prime"
+               }
+        , Case { factors  = [5, 6, 8]
+               , limit    = 150
+               , expected = 4419
+               , description = "some pairs of factors relatively prime and some not"
+               }
+        , Case { factors  = [5, 25]
+               , limit    = 51
+               , expected = 275
+               , description = "one factor is a multiple of another"
+               }
+        , Case { factors  = [43, 47]
+               , limit    = 10000
+               , expected = 2203160
+               , description = "much larger factors"
+               }
+        , Case { factors  = [1]
+               , limit    = 100
+               , expected = 4950
+               , description = "all numbers are multiples of 1"
+               }
+        , Case { factors  = []
+               , limit    = 10000
+               , expected = 0
+               , description = "no factors means an empty sum"
+               }
+        , Case { factors  = [0]
+               , limit    = 1
+               , expected = 0
+               , description = "the only multiple of 0 is 0"
+               }
+        , Case { factors  = [3, 0]
+               , limit    = 4
+               , expected = 3
+               , description = "the factor 0 does not affect the sum of multiples of other factors"
+               }
+        , Case { factors  = [2, 3, 5, 7, 11]
+               , limit    = 10000
+               , expected = 39614537
+               , description = "solutions using include-exclude must extend to cardinality greater than 3"
+               }
+        ]