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Add HeterogenousArrayLog (#173)
* Add HeterogenousArrayLog * Regenerate readme * Add additional comments clarifying some things * Port comment explaining why Variant needs to be used to recipe Readme * Reword description to note exceptional nature of this approach * Add sum type version to compare with Variant version * Cleanup comment readability * purty formatting * Simplify examples Co-authored-by: Miles Frain <[email protected]>
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‎README.md

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| | :heavy_check_mark: | [HelloHalogenHooks](recipes/HelloHalogenHooks) | A Halogen port of the ["HTML - Hello" Elm Example](https://elm-lang.org/examples/hello). |
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| | :heavy_check_mark: | [HelloReactHooks](recipes/HelloReactHooks) | A React port of the ["HTML - Hello" Elm Example](https://elm-lang.org/examples/hello). |
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| :heavy_check_mark: | :heavy_check_mark: | [HelloWorldLog](recipes/HelloWorldLog) | This recipe shows how to run a simple "Hello world!" program in either the node.js or web browser console. |
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| :heavy_check_mark: | :heavy_check_mark: | [HeterogenousArrayLog](recipes/HeterogenousArrayLog) | This recipe demonstrates how to create a heterogenous array and process its elements. |
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| | :heavy_check_mark: | [ImagePreviewsHalogenHooks](recipes/ImagePreviewsHalogenHooks) | A Halogen port of the ["Files - Drag-and-Drop" Elm Example](https://elm-lang.org/examples/drag-and-drop). |
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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). |

‎recipes/HeterogenousArrayLog/.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/HeterogenousArrayLog/README.md

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# HeterogenousArrayLog
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This recipe demonstrates how to create a heterogenous array and process its elements.
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PureScript arrays are _homogeneous_, meaning that all values must have the same type. If you want to store values with different types in the same array (i.e. a _heterogeneous_ array), you should wrap all the types you wish to store in either a [sum type](https://github.com/purescript/documentation/blob/master/language/Types.md#tagged-unions) or a [Variant](https://pursuit.purescript.org/packages/purescript-variant). This recipe demonstrates both strategies.
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## Expected Behavior:
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Prints the following:
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```
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---- Using Sum Type ----
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["a String value","4","true","false","82.4"]
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---- Using Variant Type ----
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["a String value","4","true","false","82.4"]
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```

‎recipes/HeterogenousArrayLog/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/HeterogenousArrayLog/spago.dhall

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{ name = "HeterogenousArrayLog"
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, dependencies =
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[ "console", "effect", "psci-support", "variant", "arrays" ]
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, packages = ../../packages.dhall
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, sources = [ "recipes/HeterogenousArrayLog/src/**/*.purs" ]
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}
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{-
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sources does not work with paths relative to this config
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sources = [ "src/**/*.purs" ]
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Paths must be relative to where this command is run
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-}

‎recipes/HeterogenousArrayLog/src/Main.purs

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module HeterogenousArrayLog.Main where
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import Prelude
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import Data.Functor.Variant (SProxy(..))
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import Data.Variant (Variant)
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import Data.Variant as Variant
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import Effect (Effect)
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import Effect.Class.Console (logShow)
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import Effect.Console (log)
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main :: Effect Unit
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main = do
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log "---- Using Sum Type ----"
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heterogenousArrayViaSumType
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log "\n---- Using Variant Type ----"
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heterogenousArrayViaVariant
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-------------- Sum Type Example --------------
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--
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-- Sum Type for array elements
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data SumType
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= Str String
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| Integer Int
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| Bool Boolean
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| Num Number
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heterogenousArrayViaSumType :: Effect Unit
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heterogenousArrayViaSumType = do
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let
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-- Create array
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heterogenousArray :: Array SumType
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heterogenousArray =
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[ Str "a String value"
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, Integer 4
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, Bool true
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, Bool false
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, Num 82.4
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]
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-- Demonstrate how to process array elements with a function
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-- that converts values of our SumType to strings for logging.
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-- Note, you could create a Show instance for SumType instead.
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showElement :: SumType -> String
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showElement = case _ of
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Str s -> s
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Integer i -> show i
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Bool b -> show b
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Num n -> show n
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--
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-- Show array
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logShow $ map showElement heterogenousArray
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-------------- Variant Type Example --------------
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--
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-- Variant Type for array elements
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-- Created from a "row type" of tags and other types
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type VariantType
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= Variant
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( typeLevelString :: String
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, int :: Int
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, boolean :: Boolean
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, "this type level string must match the label of the row" :: Number
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)
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heterogenousArrayViaVariant :: Effect Unit
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heterogenousArrayViaVariant = do
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let
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-- Setup some SProxy values with types matching those found within our VariantType
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--
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-- Read: "This particular `SProxy` value has the type
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-- `SProxy "typeLevelString"`..."
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_typeLevelString :: SProxy "typeLevelString"
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_typeLevelString = SProxy
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-- ... which differs from `SProxy "int"` and the other SProxy types below.
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-- Note that we can write these on one line as:
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_intValue = (SProxy :: SProxy "int")
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-- This shorthand style is also allowed:
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_boolean = (SProxy :: _ "boolean")
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-- Any string may be used as a type-level label
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_arbitraryTypeLevelString = (SProxy :: _ "this type level string must match the label of the row")
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-- Create array
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heterogenousArray :: Array VariantType
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heterogenousArray =
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-- To create a value of type `Variant`, we must inject a value into
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-- the data type using a type-level string that refers to the
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-- corresponding row (i.e. a label-type association)
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[ Variant.inj _typeLevelString "a String value"
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, Variant.inj _intValue 4
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, Variant.inj _boolean true
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-- You may also skip creating the SProxy helper values, and just write them inline:
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, Variant.inj (SProxy :: _ "boolean") false
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, Variant.inj _arbitraryTypeLevelString 82.4
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]
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-- Demonstrate how to process array elements with a function
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-- that converts values of our VariantType to strings for logging.
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-- Note, you could create a Show instance for VariantType instead.
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showElement :: VariantType -> String
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showElement =
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Variant.case_
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# Variant.on _typeLevelString identity
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# Variant.on (SProxy :: _ "int") show -- inline example
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# Variant.on _boolean show
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# Variant.on _arbitraryTypeLevelString show
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--
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-- Show array
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logShow $ map showElement heterogenousArray

‎recipes/HeterogenousArrayLog/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>HeterogenousArrayLog</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/HeterogenousArrayLog/web/index.js

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

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