Created
June 19, 2015 21:41
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comp.js
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| const reduce = Array.reduce; | |
| // Call function `f` with value `x`. | |
| const callWith = (x, f) => f(x); | |
| // Pipe value `x` through many single-argument functions in succession. | |
| // This is kind of like a Unix pipe. The value of the previous function is | |
| // passed to the next function, etc. Note that functions are called | |
| // from left-to-right, with left being first. | |
| export const pipe = (x, ...f) => reduce(f, callWith, x); | |
| // Combine a list of one-argument functions into a single one-argument function | |
| // that will pipe `x` through each function. | |
| // This is like the classic `compose` function, but goes from left-to-right | |
| // instead of right-to-left. | |
| // Returns a function. | |
| export const chain = (...f) => (x) => pipe(x, ...f); | |
| // Compose 2 functions. | |
| const comp2 = (z, y) => (x) => z(y(x)); | |
| // Classic RTL function composition. | |
| export const comp = (f, ...fn) => reduce(fn, comp2, f); |
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Forget method chaining with this one weird tip!