6 files changed, 97 insertions, 0 deletions
diff --git a/stack.yaml b/stack.yaml
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+++ b/stack.yaml
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+# Use LTS of Stackage for GHC 8.4.4
+# https://www.stackage.org/lts-16.26
+resolver: lts-16.26
+# Local packages
+packages:
+  - ./template
diff --git a/stack.yaml.lock b/stack.yaml.lock
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+++ b/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
+
+snapshots:
+- original: lts-16.26
+  completed:
+    sha256: cdbc5db9c1afe80a5998247939027a0c7db92fa0f20b5cd01596ec3da628b622
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/16/26.yaml
+    size: 533252
+packages: []
diff --git a/template/package.yaml b/template/package.yaml
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+++ b/template/package.yaml
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+name: template
+version: 0.1.0
+description: A Haskell project template for use with Stack.
+dependencies:
+  - base
+library:
+  source-dirs: ./src/lib
+executable:
+  source-dirs: ./src/exe
+  main: Main
+  dependencies:
+    - template
diff --git a/template/src/exe/Main.hs b/template/src/exe/Main.hs
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+++ b/template/src/exe/Main.hs
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+{-# LANGUAGE ScopedTypeVariables #-}
+
+module Main where
+
+import           System.Environment             ( getArgs )
+import           Template                       ( fib )
+
+main :: IO ()
+main = do
+  -- https://lotz84.github.io/haskellbyexample/ex/command-line-arguments
+  args <- getArgs
+  let arg = head args
+
+  -- https://stackoverflow.com/a/20667721
+  print (fib (read arg :: Int))
diff --git a/template/src/lib/Template.hs b/template/src/lib/Template.hs
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+++ b/template/src/lib/Template.hs
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+module Template
+  ( fib
+  ) where
+
+import           Data.Bits
+import           Data.List
+
+-- https://wiki.haskell.org/The_Fibonacci_sequence
+fib :: Int -> Integer
+fib n =
+  snd
+    . foldl_ fib_ (1, 0)
+    . dropWhile not
+    $ [ testBit n k | k <- let s = bitSize n in [s - 1, s - 2 .. 0] ]
+ where
+  fib_ (f, g) p | p         = (f * (f + 2 * g), ss)
+                | otherwise = (ss, g * (2 * f - g))
+    where ss = f * f + g * g
+  foldl_ = foldl' -- '
diff --git a/template/template.cabal b/template/template.cabal
new file mode 100644
index 0000000..13b0e48
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+++ b/template/template.cabal
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+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.34.4.
+--
+-- see: https://github.com/sol/hpack
+
+name:           template
+version:        0.1.0
+description:    A Haskell project template for use with Stack.
+build-type:     Simple
+
+library
+  exposed-modules:
+      Template
+  other-modules:
+      Paths_template
+  hs-source-dirs:
+      ./src/lib
+  build-depends:
+      base
+  default-language: Haskell2010
+
+executable template
+  main-is: Main.hs
+  other-modules:
+      Paths_template
+  hs-source-dirs:
+      ./src/exe
+  ghc-options: -main-is Main
+  build-depends:
+      base
+    , template
+  default-language: Haskell2010