lambda-calculus | 易学教程

What does eta reduce mean in the context of HLint

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问题 I'm looking at the tutorial http://haskell.org/haskellwiki/How_to_write_a_Haskell_program import System.Environment main :: IO () main = getArgs >>= print . haqify . head haqify s = "Haq! " ++ s When running this program under HLint it gives the following error; ./Haq.hs:11:1: Warning: Eta reduce Found: haqify s = "Haq! " ++ s Why not: haqify = ("Haq! " ++ ) Can someone shed some light on what exactly "Eta Reduce" means in this context? 回答1: Eta reduction is turning \x -> f x into f as long

“What part of Hindley-Milner do you not understand?”

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I swear there used to be a T-shirt for sale featuring the immortal words: What part of do you not understand? In my case, the answer would be... all of it! In particular, I often see notation like this in Haskell papers, but I have no clue what any of it means. I have no idea what branch of mathematics it's supposed to be. I recognise the letters of the Greek alphabet of course, and symbols such as "∉" (which usually means that something is not an element of a set). On the other hand, I've never seen "⊢" before ( Wikipedia claims it might mean "partition" ). I'm also unfamiliar with the use of

How to correctly curry a function in JavaScript?

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I wrote a simple curry function in JavaScript which works correctly for most cases: const add = curry((a, b, c) => a + b + c); const add2 = add(2); const add5 = add2(3); console.log(add5(5)); <script> const curried = Symbol("curried"); Object.defineProperty(curry, curried, { value: true }); function curry(functor, ...initArgs) { if (arguments.length === 0) return curry; if (typeof functor !== "function") { const value = JSON.stringify(functor); throw new TypeError(`${value} is not a function`); } if (functor[curried] || initArgs.length >= functor.length) return functor(...initArgs); const

non recursive lambda calculus factorial function

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问题 How to write a factorial function without use of recursion using lambda calculus? Meaning just the math notation not implementation in any particular programming language. 回答1: If by "without the use of recursion" you mean without general recursion and hence without fixpoints (or self applications), we can simply observe that the factorial function is primitive recursive (that is, iterative, in essence), and there is a very general and simple encoding of primitive recursion by means of

How to correctly curry a function in JavaScript?

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问题 I wrote a simple curry function in JavaScript which works correctly for most cases: const add = curry((a, b, c) => a + b + c); const add2 = add(2); const add5 = add2(3); console.log(add5(5)); <script> const curried = Symbol(\"curried\"); Object.defineProperty(curry, curried, { value: true }); function curry(functor, ...initArgs) { if (arguments.length === 0) return curry; if (typeof functor !== \"function\") { const value = JSON.stringify(functor); throw new TypeError(`${value} is not a

“What part of Hindley-Milner do you not understand?”

阅读更多关于 “What part of Hindley-Milner do you not understand?”

问题 I swear there used to be a T-shirt for sale featuring the immortal words: What part of do you not understand? In my case, the answer would be... all of it! In particular, I often see notation like this in Haskell papers, but I have no clue what any of it means. I have no idea what branch of mathematics it\'s supposed to be. I recognise the letters of the Greek alphabet of course, and symbols such as \"∉\" (which usually means that something is not an element of a set). On the other hand, I\