Why Haskell

Monads, also known as Kleisli triples in Category Theory, are an (endo-)functor together with two natural transformations, which are surprisingly useful in pure languages like Haskell, but this talk will NOT reference monads. Ever. (Well, at least not in this talk.)

Instead what I intend to impress upon an audience of newcomers to Haskell is the wide array of freely available libraries most of which is liberally licensed open source software, intuitive package management, practical build tools, reasonable documentation (when you know how to read it and where to find it), interactive shell (or REPL), mature compiler, stable runtime, testing tools that will blow your mind away, and a small but collaborative and knowledgeable community of developers. Oh, and some special features of Haskell - the language - too!

Transcript

1. Why Haskell? Susan Potter March 2012
2. What is Haskell? Figure: "pure functional, lazy, polymorphic, statically and strongly typed with type inference . . . "
3. How can I drive this thing? Figure: Photo from "If programming languages were cars" blog post http://machinegestalt.posterous.com/if-programming-languages-were-cars
4. Can I drive Haskell without all this? Figure: No need to know Category Theory proofs, just some intuitions!
5. # finger $(whoami) Login: susan Name: Susan Potter Directory: /home/susan Shell: /bin/zsh Practicing since 1997-09-29 21:18 (GMT) on tty1 from :0 Too much unread mail on me@susanpotter.net Now working at Desk.com! Looking for smart developers!;) Plan: github: mbbx6spp twitter: @SusanPotter
6. Are we "doing it wrong"? Figure: Maybe! ;) http://absolutelymadness.tumblr.com/post/17567574522
7. Overview: Choosing a language Many considerations political, human, technical Runtime performance, reliability, configurability Knowledge culture, mindshare, resources, signal to noise ratio Tooling development, build/release, configuration, deployment
8. Overview: Choosing a language Many considerations political, human, technical Runtime performance, reliability, configurability Knowledge culture, mindshare, resources, signal to noise ratio Tooling development, build/release, configuration, deployment
9. Overview: Choosing a language Many considerations political, human, technical Runtime performance, reliability, configurability Knowledge culture, mindshare, resources, signal to noise ratio Tooling development, build/release, configuration, deployment
10. Overview: Choosing a language Many considerations political, human, technical Runtime performance, reliability, configurability Knowledge culture, mindshare, resources, signal to noise ratio Tooling development, build/release, configuration, deployment
11. Overview: Agenda My Claims / Hypotheses Laziness, Functional, Type System Toolkit & Runtime Library Ecosystem Pitfalls & Hurdles
12. My Claims Performance is reasonable on par with Java and C# Mono; 2-3x CPU times of C (approx); BUT always doubt benchmarks http://shootout.alioth.debian.org/u64q/haskell.php Productivity with long-term benefits after initial steep learning curve Haskell types offer stronger verifiability strong and meaningful checks applied Pure functional code is easier to test probably not controversial
13. My Claims Performance is reasonable on par with Java and C# Mono; 2-3x CPU times of C (approx); BUT always doubt benchmarks http://shootout.alioth.debian.org/u64q/haskell.php Productivity with long-term benefits after initial steep learning curve Haskell types offer stronger verifiability strong and meaningful checks applied Pure functional code is easier to test probably not controversial
14. My Claims Performance is reasonable on par with Java and C# Mono; 2-3x CPU times of C (approx); BUT always doubt benchmarks http://shootout.alioth.debian.org/u64q/haskell.php Productivity with long-term benefits after initial steep learning curve Haskell types offer stronger verifiability strong and meaningful checks applied Pure functional code is easier to test probably not controversial
15. My Claims Performance is reasonable on par with Java and C# Mono; 2-3x CPU times of C (approx); BUT always doubt benchmarks http://shootout.alioth.debian.org/u64q/haskell.php Productivity with long-term benefits after initial steep learning curve Haskell types offer stronger verifiability strong and meaningful checks applied Pure functional code is easier to test probably not controversial
16. Haskell "lazy" by default Figure: Photo by Mark Fischer http://www.flickr.com/photos/tom_ruaat/4431626234/
17. Haskell "lazy" by default Figure: Photo by Mark Fischer http://www.flickr.com/photos/tom_ruaat/4431626234/ (jarring for mainstream programmers)
18. Example: doubleSum 3 (2 + 3) Call by value doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
19. Example: doubleSum 3 (2 + 3) Call by value doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
20. Example: doubleSum 3 (2 + 3) Call by value doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
21. Example: doubleSum 3 (2 + 3) Call by value doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
22. Example: doubleSum 3 (2 + 3) Call by value doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
23. Example: doubleSum 3 (2 + 3) Call by value doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
24. Example: doubleSum 3 (2 + 3) Call by value (evaluates inner-most expressions first) doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
25. Example: doubleSum 3 (2 + 3) Call by value (evaluates inner-most expressions first) doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
26. Example: doubleSum 3 (2 + 3) Call by value (evaluates inner-most expressions first) doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
27. Example: doubleSum 3 (2 + 3) Call by value (evaluates inner-most expressions first) doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
28. Example: doubleSum 3 (2 + 3) Call by value (evaluates inner-most expressions first) doubleSum 3 (2 + 3) → doubleSum 3 5 → 2 * (3 + 5) → 2 * 8 → 16 Call by name (evaluates outer-most expressions first) doubleSum 3 (2 + 3) → (λ x -> 2 * (3 + x)) (2 + 3)
29. Laziness in Haskell is . . . CallByName + SharingOptimization + PossibleMinorOverhead
30. Laziness: Buyer Beware filter (λ x → x < 6) [1..] (never terminates) takeWhile (λ x → x < 6) [1..] (does terminate) dropWhile (λ x → x >= 6) [1..] (does not terminate) Need to understand implications of laziness on functions Laziness with I/O implications lazy I/O with handles is problematic, but iteratee idiom solves most of these. There are a number of libraries available to help with this: enumerator, pipes, . . .
31. Laziness: Buyer Beware filter (λ x → x < 6) [1..] (never terminates) takeWhile (λ x → x < 6) [1..] (does terminate) dropWhile (λ x → x >= 6) [1..] (does not terminate) Need to understand implications of laziness on functions Laziness with I/O implications lazy I/O with handles is problematic, but iteratee idiom solves most of these. There are a number of libraries available to help with this: enumerator, pipes, . . .
32. Laziness: Buyer Beware filter (λ x → x < 6) [1..] (never terminates) takeWhile (λ x → x < 6) [1..] (does terminate) dropWhile (λ x → x >= 6) [1..] (does not terminate) Need to understand implications of laziness on functions Laziness with I/O implications lazy I/O with handles is problematic, but iteratee idiom solves most of these. There are a number of libraries available to help with this: enumerator, pipes, . . .
33. Laziness: Buyer Beware filter (λ x → x < 6) [1..] (never terminates) takeWhile (λ x → x < 6) [1..] (does terminate) dropWhile (λ x → x >= 6) [1..] (does not terminate) Need to understand implications of laziness on functions Laziness with I/O implications lazy I/O with handles is problematic, but iteratee idiom solves most of these. There are a number of libraries available to help with this: enumerator, pipes, . . .
34. Laziness: Buyer Beware filter (λ x → x < 6) [1..] (never terminates) takeWhile (λ x → x < 6) [1..] (does terminate) dropWhile (λ x → x >= 6) [1..] (does not terminate) Need to understand implications of laziness on functions Laziness with I/O implications lazy I/O with handles is problematic, but iteratee idiom solves most of these. There are a number of libraries available to help with this: enumerator, pipes, . . .
35. Laziness: Also Pretty Suuweeeet! Infinite sequences/lists made possible Recursive functions become practical Recursive types become simple Much more as well ...
36. Laziness: Also Pretty Suuweeeet! Infinite sequences/lists made possible Recursive functions become practical Recursive types become simple Much more as well ...
37. Laziness: Also Pretty Suuweeeet! Infinite sequences/lists made possible Recursive functions become practical Recursive types become simple Much more as well ...
38. Laziness: Also Pretty Suuweeeet! Infinite sequences/lists made possible Recursive functions become practical Recursive types become simple Much more as well ...
39. Purity + Laziness=> Reasoning Equality (referential transparency) Can replace occurrences of LHS with RHS Higher Order Functions encourage exploitation of higher-level patterns Function Composition leads to greater reuse
40. Purity + Laziness=> Reasoning Equality (referential transparency) Can replace occurrences of LHS with RHS Higher Order Functions encourage exploitation of higher-level patterns Function Composition leads to greater reuse
41. Purity + Laziness=> Reasoning Equality (referential transparency) Can replace occurrences of LHS with RHS Higher Order Functions encourage exploitation of higher-level patterns Function Composition leads to greater reuse
42. mysum :: Num a => [a] -> a mysum xs = foldr (+) 0 xs myproduct :: Num a => [a] -> a myproduct xs = foldr (*) 1 xs myany :: (a -> Bool) -> [a] -> Bool myany pred xs = foldr (\ x b -> b || pred x) False xs myall :: (a -> Bool) -> [a] -> Bool myall pred xs = foldr (\ x b -> b && pred x) True xs
43. mysum :: Num a => [a] -> a mysum xs = foldr (+) 0 xs myproduct :: Num a => [a] -> a myproduct xs = foldr (*) 1 xs myany :: (a -> Bool) -> [a] -> Bool myany pred xs = foldr (\ x b -> b || pred x) False xs myall :: (a -> Bool) -> [a] -> Bool myall pred xs = foldr (\ x b -> b && pred x) True xs
44. mysum :: Num a => [a] -> a mysum xs = foldr (+) 0 xs myproduct :: Num a => [a] -> a myproduct xs = foldr (*) 1 xs myany :: (a -> Bool) -> [a] -> Bool myany pred xs = foldr (\ x b -> b || pred x) False xs myall :: (a -> Bool) -> [a] -> Bool myall pred xs = foldr (\ x b -> b && pred x) True xs
45. mysum :: Num a => [a] -> a mysum xs = foldr (+) 0 xs myproduct :: Num a => [a] -> a myproduct xs = foldr (*) 1 xs myany :: (a -> Bool) -> [a] -> Bool myany pred xs = foldr (\ x b -> b || pred x) False xs myall :: (a -> Bool) -> [a] -> Bool myall pred xs = foldr (\ x b -> b && pred x) True xs
46. mysum :: Num a => [a] -> a mysum xs = foldr (+) 0 xs myproduct :: Num a => [a] -> a myproduct xs = foldr (*) 1 xs myany :: (a -> Bool) -> [a] -> Bool myany pred xs = foldr (\ x b -> b || pred x) False xs myall :: (a -> Bool) -> [a] -> Bool myall pred xs = foldr (\ x b -> b && pred x) True xs
47. mysum :: Num a => [a] -> a mysum xs = foldr (+) 0 xs myproduct :: Num a => [a] -> a myproduct xs = foldr (*) 1 xs myany :: (a -> Bool) -> [a] -> Bool myany pred xs = foldr (\ x b -> b || pred x) False xs myall :: (a -> Bool) -> [a] -> Bool myall pred xs = foldr (\ x b -> b && pred x) True xs
48. mysum :: Num a => [a] -> a mysum xs = foldr (+) 0 xs myproduct :: Num a => [a] -> a myproduct xs = foldr (*) 1 xs myany :: (a -> Bool) -> [a] -> Bool myany pred xs = foldr (\ x b -> b || pred x) False xs myall :: (a -> Bool) -> [a] -> Bool myall pred xs = foldr (\ x b -> b && pred x) True xs
49. class Monoid m where mappend :: m -> m -> m mempty :: m instance Num a => Monoid a where mappend :: m -> m -> m mappend x y = (+) x y mempty :: m mempty = 0 instance Monoid Bool where mappend :: m -> m -> m mappend True _ = True mappend _ True = True mappend _ _ = False mempty :: m
50. class Monoid m where mappend :: m -> m -> m mempty :: m instance Num a => Monoid a where mappend :: m -> m -> m mappend x y = (+) x y mempty :: m mempty = 0 instance Monoid Bool where mappend :: m -> m -> m mappend True _ = True mappend _ True = True mappend _ _ = False mempty :: m
51. class Monoid m where mappend :: m -> m -> m mempty :: m instance Num a => Monoid a where mappend :: m -> m -> m mappend x y = (+) x y mempty :: m mempty = 0 instance Monoid Bool where mappend :: m -> m -> m mappend True _ = True mappend _ True = True mappend _ _ = False mempty :: m
52. Haskell type signatures can . . . express side effects e.g. String -> IO Int declare computational strategies e.g. Num a => [a] -> Sum a impose constraints e.g. Num a => a -> a question value availability e.g. String -> Maybe Int verify client-server protocol dialogs? an exercise for reader ;)
53. Haskell type signatures can . . . express side effects e.g. String -> IO Int declare computational strategies e.g. Num a => [a] -> Sum a impose constraints e.g. Num a => a -> a question value availability e.g. String -> Maybe Int verify client-server protocol dialogs? an exercise for reader ;)
54. Haskell type signatures can . . . express side effects e.g. String -> IO Int declare computational strategies e.g. Num a => [a] -> Sum a impose constraints e.g. Num a => a -> a question value availability e.g. String -> Maybe Int verify client-server protocol dialogs? an exercise for reader ;)
55. Haskell type signatures can . . . express side effects e.g. String -> IO Int declare computational strategies e.g. Num a => [a] -> Sum a impose constraints e.g. Num a => a -> a question value availability e.g. String -> Maybe Int verify client-server protocol dialogs? an exercise for reader ;)
56. Haskell type signatures can . . . express side effects e.g. String -> IO Int declare computational strategies e.g. Num a => [a] -> Sum a impose constraints e.g. Num a => a -> a question value availability e.g. String -> Maybe Int verify client-server protocol dialogs? an exercise for reader ;)
57. Interfaces in OO . . . Figure: Class definitions are married to the interfaces they implement.
58. Interfaces in Haskell: Typeclasses. . . Decouple type definition from interface Allow upstream implementations Extend thirdparty libraries easily Redefine implementations upstream No meaningless "any type" functions Very flexible
59. Interfaces in Haskell: Typeclasses. . . Decouple type definition from interface Allow upstream implementations Extend thirdparty libraries easily Redefine implementations upstream No meaningless "any type" functions Very flexible
60. Interfaces in Haskell: Typeclasses. . . Decouple type definition from interface Allow upstream implementations Extend thirdparty libraries easily Redefine implementations upstream No meaningless "any type" functions Very flexible
61. Interfaces in Haskell: Typeclasses. . . Decouple type definition from interface Allow upstream implementations Extend thirdparty libraries easily Redefine implementations upstream No meaningless "any type" functions Very flexible
62. Interfaces in Haskell: Typeclasses. . . Decouple type definition from interface Allow upstream implementations Extend thirdparty libraries easily Redefine implementations upstream No meaningless "any type" functions Very flexible
63. Interfaces in Haskell: Typeclasses. . . Decouple type definition from interface Allow upstream implementations Extend thirdparty libraries easily Redefine implementations upstream No meaningless "any type" functions Very flexible
64. class (Eq a) => Ord a where compare :: a -> a -> Ordering compare x y | x == y = EQ | x <= y = LT | otherwise = GT (<), (>), (>=), (<=) :: a -> a -> Bool ... max, min :: a -> a -> a ...
65. Typically this just works . . . data SimpleShape = Square { size :: Double } | Circle { radius :: Double } deriving (Eq, Ord, Show) We explicitly use the default definitions . . . and when it doesn’t . . . instance Ord SimpleShape where ...
66. Are you awake? Figure: http://absolutelymadness.tumblr.com/post/18126913457
67. Haskell Tooling: Libraries Quite a few Practical libraries Often freely available Permissive OSS licenses
68. Haskell Tooling: Libraries Quite a few Practical libraries Often freely available Permissive OSS licenses
69. Haskell Tooling: Libraries Quite a few Practical libraries Often freely available Permissive OSS licenses
70. Haskell Tooling: Libraries Quite a few Practical libraries Often freely available Permissive OSS licenses
71. Haskell Tooling: Runtime Reasonably performant between JVM 7 and C# Mono performance GC settings easily customized Numerous other runtime options
72. Haskell Tooling: Runtime Reasonably performant between JVM 7 and C# Mono performance GC settings easily customized Numerous other runtime options
73. Haskell Tooling: Runtime Reasonably performant between JVM 7 and C# Mono performance GC settings easily customized Numerous other runtime options
74. Haskell Tooling: Tools Testing tools QuickCheck, HUnit Documentation tools Haddock, Hoogle (lookup documentation) Build tools Cabal, cabal-dev, cabal-nirvana, see "next slide"
75. Haskell Tooling: Tools Testing tools QuickCheck, HUnit Documentation tools Haddock, Hoogle (lookup documentation) Build tools Cabal, cabal-dev, cabal-nirvana, see "next slide"
76. Haskell Tooling: Tools Testing tools QuickCheck, HUnit Documentation tools Haddock, Hoogle (lookup documentation) Build tools Cabal, cabal-dev, cabal-nirvana, see "next slide"
77. Haskell Tooling: Dependency Management Hackage database of freely available Haskell libraries Cabal great to get started, BUT . . . cabal-dev & similar provides sandboxing, list RVM with gemsets; more important for statically typed environments cabal-nirvana think compatible distribution snapshot of Hackage DB
78. Haskell Tooling: Dependency Management Hackage database of freely available Haskell libraries Cabal great to get started, BUT . . . cabal-dev & similar provides sandboxing, list RVM with gemsets; more important for statically typed environments cabal-nirvana think compatible distribution snapshot of Hackage DB
79. Haskell Tooling: Dependency Management Hackage database of freely available Haskell libraries Cabal great to get started, BUT . . . cabal-dev & similar provides sandboxing, list RVM with gemsets; more important for statically typed environments cabal-nirvana think compatible distribution snapshot of Hackage DB
80. Haskell Tooling: Dependency Management Hackage database of freely available Haskell libraries Cabal great to get started, BUT . . . cabal-dev & similar provides sandboxing, list RVM with gemsets; more important for statically typed environments cabal-nirvana think compatible distribution snapshot of Hackage DB
81. Haskell Tooling: Don’ts for Newbies Use GHC (not HUGS) Hugs written for educational purposes not industrial usage Forget what you know (imperative/OO) relearn programming in a functional-style return is a function name it does not mean return in the C/Java/C# way class does not mean OO-class think decoupled interface with optional default impelementations and a lot more power
82. Haskell Tooling: Don’ts for Newbies Use GHC (not HUGS) Hugs written for educational purposes not industrial usage Forget what you know (imperative/OO) relearn programming in a functional-style return is a function name it does not mean return in the C/Java/C# way class does not mean OO-class think decoupled interface with optional default impelementations and a lot more power
83. Haskell Tooling: Don’ts for Newbies Use GHC (not HUGS) Hugs written for educational purposes not industrial usage Forget what you know (imperative/OO) relearn programming in a functional-style return is a function name it does not mean return in the C/Java/C# way class does not mean OO-class think decoupled interface with optional default impelementations and a lot more power
84. Haskell Tooling: Don’ts for Newbies Use GHC (not HUGS) Hugs written for educational purposes not industrial usage Forget what you know (imperative/OO) relearn programming in a functional-style return is a function name it does not mean return in the C/Java/C# way class does not mean OO-class think decoupled interface with optional default impelementations and a lot more power
85. Haskell Tooling: Suggestions Explicit language extensions Intentionally and explicitly enable per module Sandbox your builds with cabal-dev or similar Think in types and shapes and use Hoogle to lookup based on types and function "shapes"
86. Haskell Tooling: Suggestions Explicit language extensions Intentionally and explicitly enable per module Sandbox your builds with cabal-dev or similar Think in types and shapes and use Hoogle to lookup based on types and function "shapes"
87. Haskell Tooling: Suggestions Explicit language extensions Intentionally and explicitly enable per module Sandbox your builds with cabal-dev or similar Think in types and shapes and use Hoogle to lookup based on types and function "shapes"
88. Oh, the possibilities! Parallel / Concurrency Options threads, dataflow, par, seq "Cloud" Haskell A kind of Erlang/OTP clone in Haskell Data Parallel Haskell GHC extensions to support nested data parallelism accounting, "Nepal" Haskell’s Foreign Function Interface (FFI) Interface with native code from Haskell GPU Programming in Haskell Obsidian, Nikola, GpuGen, numerous papers on this too Much more. . . Research meeting industrial application
89. Oh, the possibilities! Parallel / Concurrency Options threads, dataflow, par, seq "Cloud" Haskell A kind of Erlang/OTP clone in Haskell Data Parallel Haskell GHC extensions to support nested data parallelism accounting, "Nepal" Haskell’s Foreign Function Interface (FFI) Interface with native code from Haskell GPU Programming in Haskell Obsidian, Nikola, GpuGen, numerous papers on this too Much more. . . Research meeting industrial application
90. Oh, the possibilities! Parallel / Concurrency Options threads, dataflow, par, seq "Cloud" Haskell A kind of Erlang/OTP clone in Haskell Data Parallel Haskell GHC extensions to support nested data parallelism accounting, "Nepal" Haskell’s Foreign Function Interface (FFI) Interface with native code from Haskell GPU Programming in Haskell Obsidian, Nikola, GpuGen, numerous papers on this too Much more. . . Research meeting industrial application
91. Oh, the possibilities! Parallel / Concurrency Options threads, dataflow, par, seq "Cloud" Haskell A kind of Erlang/OTP clone in Haskell Data Parallel Haskell GHC extensions to support nested data parallelism accounting, "Nepal" Haskell’s Foreign Function Interface (FFI) Interface with native code from Haskell GPU Programming in Haskell Obsidian, Nikola, GpuGen, numerous papers on this too Much more. . . Research meeting industrial application
92. Oh, the possibilities! Parallel / Concurrency Options threads, dataflow, par, seq "Cloud" Haskell A kind of Erlang/OTP clone in Haskell Data Parallel Haskell GHC extensions to support nested data parallelism accounting, "Nepal" Haskell’s Foreign Function Interface (FFI) Interface with native code from Haskell GPU Programming in Haskell Obsidian, Nikola, GpuGen, numerous papers on this too Much more. . . Research meeting industrial application
93. Oh, the possibilities! Parallel / Concurrency Options threads, dataflow, par, seq "Cloud" Haskell A kind of Erlang/OTP clone in Haskell Data Parallel Haskell GHC extensions to support nested data parallelism accounting, "Nepal" Haskell’s Foreign Function Interface (FFI) Interface with native code from Haskell GPU Programming in Haskell Obsidian, Nikola, GpuGen, numerous papers on this too Much more. . . Research meeting industrial application
94. Questions? Figure: http://www.flickr.com/photos/42682395@N04/ @SusanPotter
95. Questions? Figure: http://www.flickr.com/photos/42682395@N04/ @SusanPotter
96. Bonus: References / Resources Channel 9 Lectures (Erik Meijer) http://channel9.msdn.com/Shows/Going+Deep/ Lecture-Series-Erik-Meijer-Functional-Programming-Fundamentals-Chapter-1 Learn You A Haskell http://learnyouahaskell.com Haskell Reddit http://www.reddit.com/r/haskell/ Haskell Cafe http://www.haskell.org/mailman/listinfo/haskell-cafe Real World Haskell http://book.realworldhaskell.org/
97. Bonus: References / Resources Channel 9 Lectures (Erik Meijer) http://channel9.msdn.com/Shows/Going+Deep/ Lecture-Series-Erik-Meijer-Functional-Programming-Fundamentals-Chapter-1 Learn You A Haskell http://learnyouahaskell.com Haskell Reddit http://www.reddit.com/r/haskell/ Haskell Cafe http://www.haskell.org/mailman/listinfo/haskell-cafe Real World Haskell http://book.realworldhaskell.org/
98. Bonus: References / Resources Channel 9 Lectures (Erik Meijer) http://channel9.msdn.com/Shows/Going+Deep/ Lecture-Series-Erik-Meijer-Functional-Programming-Fundamentals-Chapter-1 Learn You A Haskell http://learnyouahaskell.com Haskell Reddit http://www.reddit.com/r/haskell/ Haskell Cafe http://www.haskell.org/mailman/listinfo/haskell-cafe Real World Haskell http://book.realworldhaskell.org/
99. Bonus: References / Resources Channel 9 Lectures (Erik Meijer) http://channel9.msdn.com/Shows/Going+Deep/ Lecture-Series-Erik-Meijer-Functional-Programming-Fundamentals-Chapter-1 Learn You A Haskell http://learnyouahaskell.com Haskell Reddit http://www.reddit.com/r/haskell/ Haskell Cafe http://www.haskell.org/mailman/listinfo/haskell-cafe Real World Haskell http://book.realworldhaskell.org/
100. Bonus: References / Resources Channel 9 Lectures (Erik Meijer) http://channel9.msdn.com/Shows/Going+Deep/ Lecture-Series-Erik-Meijer-Functional-Programming-Fundamentals-Chapter-1 Learn You A Haskell http://learnyouahaskell.com Haskell Reddit http://www.reddit.com/r/haskell/ Haskell Cafe http://www.haskell.org/mailman/listinfo/haskell-cafe Real World Haskell http://book.realworldhaskell.org/
101. Bonus: Brief QuickCheck Example module Tests where import Test.QuickCheck (quickCheck) propReverseReverse :: [Char] -> Bool propReverseReverse s = (reverse . reverse) s == s excuse the weird syntax form, indenting didn’t show up ;( main = do {quickCheck propReverseReverse }