56 lines
2.4 KiB
Swift
56 lines
2.4 KiB
Swift
//
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// Curry.swift
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// WolfPipe
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//
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// Created by Wolf McNally on 11/8/18.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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/// Takes a 2-argument function and returns a function that takes
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/// the first argument and returns a function that takes the second argument
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/// and returns the result.
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///
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/// Used to take two-argument functions and produce a single-argument function for
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/// use with the pipe operator.
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public func curry<A, B, C>(_ f: @escaping (A, B) -> C) -> (A) -> (B) -> C {
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return { a in { b in f(a, b) } }
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}
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/// Takes a function taking A and returning a function that takes B and returns C,
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/// and returns a function taking B and returning a function that takes A and returns C.
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///
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/// The produced result C is the same.
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///
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/// Used for flipping the arguments of existing functions when currying.
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func flip<A, B, C>(_ f: @escaping (A) -> (B) -> C) -> (B) -> (A) -> C {
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return { b in { a in f(a)(b) } }
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}
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/// Takes a function taking A and returning a function that takes no arguments and returns C,
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/// and returns a function taking no arguments and returning a function taking A and returning C.
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func flip<A, C>(_ f: @escaping (A) -> () -> C) -> () -> (A) -> C {
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return { { a in f(a)() } }
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}
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/// Takes a function taking no arguments and returning A, calls the function and
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/// returns the result.
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func zurry<A>(_ f: () -> A) -> A {
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return f()
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}
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