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Memoize fibonacci (#187)
* Add MemoizeFibonacci * Remove Purty newlines * Undo purty squish * Move main function to top of file * Add example: which variations will break memoize function; ignore broken4 fibBroken4 fails to compile. Not sure whether this is a compiler bug or not. Co-authored-by: Jordan Martinez <[email protected]>
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‎README.md‎

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| | :heavy_check_mark: | [InterpretHalogenHooks](recipes/InterpretHalogenHooks) | Demonstrates how to use a custom monad (in this case, using `ReaderT` with `Aff` as the effect type) for a component, and then interpreting that custom monad back down to `Aff`, so it can be run as a normal component. |
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| | :heavy_check_mark: | [KeyboardInputHalogenHooks](recipes/KeyboardInputHalogenHooks) | This example demonstrates how to selectively capture keyboard events and, more generally, how to use `EventSource`s in Halogen. |
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| | :heavy_check_mark: | [LifecycleHalogenHooks](recipes/LifecycleHalogenHooks) | Demonstrates component lifecycle. |
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| :heavy_check_mark: | :heavy_check_mark: | [MemoizeFibonacci](recipes/MemoizeFibonacci) | This recipe demonstrates correct and incorrect use of the [`memoize`](https://pursuit.purescript.org/packages/purescript-memoize/docs/Data.Function.Memoize#v:memoize) function by calculating the fibonacci sequence. |
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| | :heavy_check_mark: | [NumbersHalogenHooks](recipes/NumbersHalogenHooks) | A Halogen port of the ["Random - Numbers" Elm Example](https://elm-lang.org/examples/numbers). |
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| | :heavy_check_mark: | [NumbersReactHooks](recipes/NumbersReactHooks) | A React port of the ["Random - Numbers" Elm Example](https://elm-lang.org/examples/numbers). |
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| | :heavy_check_mark: | [PositionsHalogenHooks](recipes/PositionsHalogenHooks) | A Halogen port of the ["Random - Positions" Elm Example](https://elm-lang.org/examples/positions). |

‎recipes/MemoizeFibonacci/.gitignore‎

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/bower_components/
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/node_modules/
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/.pulp-cache/
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/output/
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/generated-docs/
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/.psc-package/
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/.psc*
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/.purs*
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/.psa*
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/.spago
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/web-dist/
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/prod-dist/
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/prod/

‎recipes/MemoizeFibonacci/README.md‎

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# MemoizeFibonacci
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This recipe demonstrates correct and incorrect use of the [`memoize`](https://pursuit.purescript.org/packages/purescript-memoize/docs/Data.Function.Memoize#v:memoize) function by calculating the fibonacci sequence.
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## Expected Behavior:
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### Node.js
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Prints the following to console, which demonstrates `fibFast` is memoized correctly, while `fibSlow` is not.
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```
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basic fib result: 13
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fibFast 1: 1
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fibFast 0: 0
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fibFast 2: 1
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fibFast 3: 2
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fibFast 4: 3
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fibFast 5: 5
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fibFast 6: 8
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fibFast 7: 13
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fibFast result: 13
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fibSlow 1: 1
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 3: 2
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 1: 1
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 3: 2
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fibSlow 4: 3
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fibSlow 5: 5
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 1: 1
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 3: 2
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fibSlow 4: 3
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fibSlow 1: 1
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 3: 2
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 1: 1
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fibSlow 0: 0
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fibSlow 1: 1
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fibSlow 2: 1
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fibSlow 3: 2
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fibSlow 4: 3
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fibSlow 5: 5
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fibSlow 6: 8
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fibSlow 7: 13
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fibSlow result: 13
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```
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### Browser
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Prints same output as above to dev console when the page is loaded.
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Make sure to open the console with dev tools first, then reload/refresh the page.

‎recipes/MemoizeFibonacci/nodeSupported.md‎

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This file just indicates that the node backend is supported.
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It is used for CI and autogeneration purposes.

‎recipes/MemoizeFibonacci/spago.dhall‎

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{ name = "MemoizeFibonacci"
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, dependencies =
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[ "console", "debug", "effect", "interpolate", "memoize", "psci-support" ]
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, packages = ../../packages.dhall
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, sources = [ "recipes/MemoizeFibonacci/src/**/*.purs" ]
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}

‎recipes/MemoizeFibonacci/src/Main.purs‎

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module MemoizeFibonacci.Main where
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import Prelude
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import Data.Function.Memoize (memoize)
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import Data.Interpolate (i)
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import Debug.Trace (spy)
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import Effect (Effect)
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import Effect.Class.Console (log)
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main :: Effect Unit
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main = do
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log $ i "basic fib result: " $ fib 7
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log $ i "fibFast result: " $ fibFast 7
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log $ i "fibSlow result: " $ fibSlow 7
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-- The following variations type-check, but do not correctly memoize
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-- the functions. They are commented out intentionally. Uncomment them
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-- and run them to see for yourself.
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-- log $ i "fibBroken1 result: " $ fibBroken1 7
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-- log $ i "fibBroken2 result: " $ fibBroken2 7
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-- log $ i "fibBroken3 result: " $ fibBroken3 7
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-- Note: this one fails to compile.
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-- log $ i "fibBroken4 result: " $ fibBroken4 7
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-- Basic fibonacci implementation
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fib :: Int -> Int
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fib 0 = 0
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fib 1 = 1
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fib n = fib (n - 2) + fib (n - 1)
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--------------------------------------------------------------------------
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-- Same as `fib`, but with `spy` statements added to reveal duplicated work
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fibSlow :: Int -> Int
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fibSlow 0 = spy "fibSlow 0" 0
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fibSlow 1 = spy "fibSlow 1" 1
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fibSlow n =
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spy ("fibSlow " <> show n)
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$ fibSlow (n - 2)
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+ fibSlow (n - 1)
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--------------------------------------------------------------------------
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-- Fast memoized version of fibonacci
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fibFast :: Int -> Int
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fibFast 0 = spy "fibFast 0" 0
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fibFast 1 = spy "fibFast 1" 1
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fibFast n =
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spy ("fibFast " <> show n)
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$ fibMemo (n - 2)
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+ fibMemo (n - 1)
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fibMemo :: Int -> Int
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fibMemo = memoize \n -> fibFast n
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--------------------------------------------------------------------------
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--------------------------------------------------------------------------
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-- Broken due to the `memoize` function being written in a non-thunked form
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fibBroken1 :: Int -> Int
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fibBroken1 0 = spy "fibBroken1 0" 0
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fibBroken1 1 = spy "fibBroken1 1" 1
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fibBroken1 n =
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spy ("fibBroken1 " <> show n)
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$ fibNonThunkedMemoize (n - 2)
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+ fibNonThunkedMemoize (n - 1)
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fibNonThunkedMemoize :: Int -> Int
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fibNonThunkedMemoize n = memoize fibBroken1 n
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--------------------------------------------------------------------------
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-- Broken due to using a let clause within the function body to define
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-- memoized function rather than memoizing function outside of its body
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fibBroken2 :: Int -> Int
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fibBroken2 0 = spy "fibBroken2 0" 0
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fibBroken2 1 = spy "fibBroken2 1" 1
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fibBroken2 n =
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let
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fibLetClauseMemoize = memoize \n -> fibBroken2 n
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in spy ("fibBroken2 " <> show n)
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$ fibLetClauseMemoize (n - 2)
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+ fibLetClauseMemoize (n - 1)
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--------------------------------------------------------------------------
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-- Broken due to using a where clause within the function body to define
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-- memoized function rather than memoizing function outside of its body
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fibBroken3 :: Int -> Int
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fibBroken3 0 = spy "fibBroken3 0" 0
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fibBroken3 1 = spy "fibBroken3 1" 1
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fibBroken3 n =
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spy ("fibBroken3 " <> show n)
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$ fibWhereClauseMemoize (n - 2)
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+ fibWhereClauseMemoize (n - 1)
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where
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fibWhereClauseMemoize = memoize \n -> fibBroken3 n
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--------------------------------------------------------------------------
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-- Note: This version fails to compile completely.
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-- Broken due to the `memoize` function being written in a point-free form
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-- fibBroken4 :: Int -> Int
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-- fibBroken4 0 = spy "fibBroken4 0" 0
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-- fibBroken4 1 = spy "fibBroken4 1" 1
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-- fibBroken4 n =
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-- spy ("fibBroken4 " <> show n)
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-- $ fibPointFreeMemoize (n - 2)
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-- + fibPointFreeMemoize (n - 1)
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--
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-- fibPointFreeMemoize :: Int -> Int
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-- fibPointFreeMemoize = memoize fibBroken4

‎recipes/MemoizeFibonacci/web/index.html‎

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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="UTF-8">
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<title>MemoizeFibonacci</title>
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</head>
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<body>
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<script src="./index.js"></script>
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</body>
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</html>

‎recipes/MemoizeFibonacci/web/index.js‎

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"use strict";
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require("../../../output/MemoizeFibonacci.Main/index.js").main();

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