Add 'Intro to Haskell' content from haskell branch

Author: fanquake

README.md

@@ -1,5 +1,5 @@
 # Lunch-N-Learn
 
-Here is where we will be putting up the content for our Lunch and Learn Sessions
+Directories contain the content for our Lunch and Learn Sessions.
 
-Check the branches for the different topics covered in the sessions.
+- [Intro to Haskell](/haskell)

haskell/01/.gitignore

@@ -0,0 +1,3 @@
+.stack-work/
+Week1.cabal
+*~

haskell/01/ChangeLog.md

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+# Changelog for Week1
+
+## Unreleased changes

haskell/01/LICENSE

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+Copyright Author name here (c) 2018
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Author name here nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

haskell/01/README.md

@@ -0,0 +1 @@
+# Week1

haskell/01/Setup.hs

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+import Distribution.Simple
+main = defaultMain

haskell/01/app/Main.hs

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+module Main where
+
+import Stack
+
+main :: IO ()
+main = someFunc

haskell/01/package.yaml

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+name:                Week1
+version:             0.1.0.0
+github:              "githubuser/Week1"
+license:             BSD3
+author:              "Author name here"
+maintainer:          "[email protected]"
+copyright:           "2018 Author name here"
+
+extra-source-files:
+- README.md
+- ChangeLog.md
+
+# Metadata used when publishing your package
+# synopsis:            Short description of your package
+# category:            Web
+
+# To avoid duplicated efforts in documentation and dealing with the
+# complications of embedding Haddock markup inside cabal files, it is
+# common to point users to the README.md file.
+description:         Please see the README on GitHub at <https://github.com/githubuser/Week1#readme>
+
+dependencies:
+- base >= 4.7 && < 5
+
+library:
+  source-dirs: src
+
+executables:
+  Week1-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - Week1
+
+tests:
+  Week1-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - Week1

haskell/01/src/ADT.hs

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+module ADT where
+
+data TrafficLight = Green | Amber | Red
+
+instance Show TrafficLight where
+    show Green = "Green"
+    show Amber = "Amber"
+    show Red   = "Red"
+
+one_step_down :: TrafficLight -> TrafficLight
+one_step_down Green = Amber
+one_step_down Amber = Red
+one_step_down Red = Red
+
+one_step_up :: TrafficLight -> TrafficLight
+one_step_up Green = Green
+one_step_up Amber = Green
+one_step_up Red   = Amber
+
+
+stop_cars :: TrafficLight -> TrafficLight
+stop_cars Green = stop_cars (one_step_down Green)
+stop_cars Amber = one_step_down Amber
+stop_cars Red =    Red

haskell/01/src/AdvancedStack.hs

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+{-# LANGUAGE GADTs #-}
+
+module AdvancedStack where
+
+import Data.Function ((&))
+
+
+data Z
+data S n
+
+data Stack n a where
+    Empty :: Stack Z a
+    Top   :: a -> Stack m a -> Stack (S m) a
+
+instance Show a => Show (Stack n a) where
+    show (Empty) = "Empty]"
+    show (Top a s) = "[" ++ show a ++ "," ++ show s 
+
+instance Functor (Stack n) where
+    fmap f Empty = Empty
+    fmap f (Top a s) = (Top $ f a) $ fmap f s
+
+pop :: Stack (S n) a -> (a, Stack n a)
+pop (Top a s) = (a , s)
+
+peek :: Stack (S n) a -> (a, Stack (S n) a)
+peek t@(Top a s) = (a, t)
+
+push :: a -> Stack n a -> Stack (S n) a
+push a s  = Top a s
+
+safe_DoublePop :: Num a =>  Stack (S (S n)) a -> (a, Stack n a)
+safe_DoublePop s = (pop s) & snd & pop
+
+safe_do_stuff :: Integer
+safe_do_stuff = fst $ safe_DoublePop start
+    where
+        start = push 2 Empty

haskell/01/src/Stack.hs

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+module Stack_bak where
+
+data Stack a = Empty | Cons a (Stack a)
+
+instance Show a => Show (Stack a) where
+    show (Empty) = "Empty]"
+    show (Cons a s) = "[" ++ show a ++ "," ++ show s
+
+
+instance Functor Stack where
+    fmap f (Cons a s) = Cons (f a) (fmap f s)
+    fmap _ (Empty) = Empty
+
+someFunc :: IO ()
+someFunc = putStrLn "someFunc"
+
+push :: a -> Stack a -> Stack a
+push x (Cons y s) = Cons x (Cons y s)
+push x Empty      = Cons x (Empty)
+
+pop :: Stack a -> (a, Stack a)
+pop (Cons y s) = (y,s)
+pop Empty      = error "POPPING EMPTY STACK"
+
+chainContext :: (a, Stack a) -> (Stack a -> (a, Stack a)) -> (a,Stack a)
+chainContext (_,s) f = f s
+
+peek :: Stack a -> (a,Stack a)
+peek stack@(Cons y _) = (y ,stack)
+peek Empty = error "Peeking Empty list"
+
+doublePop :: Num a =>  Stack a -> (a, Stack a)
+doublePop s = (pop s) `chainContext` pop 
+
+do_stuff :: Integer
+do_stuff = fst $ doublePop start
+    where
+        start = push 2 Empty
+        

haskell/01/stack.yaml

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+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# Resolver to choose a 'specific' stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+# resolver: ghcjs-0.1.0_ghc-7.10.2
+#
+# The location of a snapshot can be provided as a file or url. Stack assumes
+# a snapshot provided as a file might change, whereas a url resource does not.
+#
+# resolver: ./custom-snapshot.yaml
+# resolver: https://example.com/snapshots/2018-01-01.yaml
+resolver: lts-12.10
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+# - location:
+#    git: https://github.com/commercialhaskell/stack.git
+#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#  subdirs:
+#  - auto-update
+#  - wai
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the resolver
+# using the same syntax as the packages field.
+# (e.g., acme-missiles-0.3)
+# extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+# flags: {}
+
+# Extra package databases containing global packages
+# extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=1.7"
+#
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor

haskell/01/test/Spec.hs

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+main :: IO ()
+main = putStrLn "Test suite not yet implemented"

haskell/README.md

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+# Lunch-N-Learn: Haskell
+
+
+## Installing Haskell
+
+```brew install haskell-stack```
+
+This will include Stack, the build tool we will be using to ensure we don't end up in dependency hell thanks to Cabal
+
+## Installing Haskero for VS Code
+
+Haskell development (especially at the start) can be tedious if you need to run ghc everytime to see if you types compose. Running Haskero with VS Code allows us to do type checking within our editor
+
+- Install vscode (https://code.visualstudio.com/)
+- Install 'code' in your $PATH to make it easier to open VSCode (https://code.visualstudio.com/docs/setup/mac)
+- Search for and install **Haskero** from the list of extensions in VSCode
+- Run ```stack build intero``` within a stack project
+- Re-launch VSCode using ```code .```
+
+## Running the week's code
+
+Each week's project code will be its own self-contained Stack project
+
+``` cd <project-file> ```
+
+``` stack build ``` --> Builds the executables
+
+```stack ghci``` --> To access the GHC REPL
+
+