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Christoph Hegemann
kritzcreek
Passionate typed functional programmer. Member of the church of Emacs.
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In PureScript there are types of different kinds. Kinds are types for types. For example Int has kind Type, and we write it as Int :: Type. You can ask for the kind of a type in purs psci
>:k IntType
Type constructors take types to other types. For example Array (which still needs another type to form a type a value could have, like Array Int):
Generating collections of random numbers in PureScript
A problem that I've seen beginners run into in Haskell or PureScript a couple of times now is how to generate a List of random numbers. It's a common requirement for little games (which make for great first projects) to generate these, and it definitely seems to be a stumbling block.
Why are random numbers hard?
Randomness is considered a side effect in purely functional languages, which means that to generate them you usually need access to Eff/IO, which in turn means we need to deal with Monads. And while generating a single random number is usually pretty easy with do-notation, the typical intuition beginners have built when going from single values to a collection is to use map, but that fails.
One particular argument, that I've heard come up multiple times now, is that teachers are complaining about the length function being polymorphic. Apparently length :: forall a. Foldable f => f a -> Int is hard to grasp/understand/accept for a new-comer. The solutions proposed to solve this problem are to:
Return length to its non-Foldable type
Use a custom Prelude to teach beginners
Drawbacks for 1 include that practicioners like the fact that length works for all kinds of data structures, and don't want that taken away from them. The primary problem with solution 2 is that students can't go and use their aquired knowledge to work on Open
Purescript - Read a file from disc with the browser API
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This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
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This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
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