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Address @i-am-tom and @shineli1984's review

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Steve Mao 2017-04-10 21:08:44 +10:00
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@ -698,7 +698,7 @@ pairToCoords(coordsToPair({x: 1, y: 2})) // {x: 1, y: 2}
### Catamorphism ### Catamorphism
A `reduceRight` function. Take a bunch of things, and combine them into another. The morphism is from "bunch of things" to "another". A `reduceRight` function that applies a function against an accumulator and each value of the array (from right-to-left) to reduce it to a single value.
```js ```js
const sum = xs => xs.reduceRight((acc, x) => acc + x, 0) const sum = xs => xs.reduceRight((acc, x) => acc + x, 0)
@ -734,17 +734,22 @@ The combination of anamorphism and catamorphism.
### Paramorphism ### Paramorphism
Enhancement of catamorphism. It's like `reduceRight`. However, there's a difference: A function just like `reduceRight`. However, there's a difference:
In paramorphism, your reducer's arguments are the current value, the reduction of all previous values, and the list of values that formed that reduction. In paramorphism, your reducer's arguments are the current value, the reduction of all previous values, and the list of values that formed that reduction.
```js ```js
// Obviously not safe for lists containing `undefined`, // Obviously not safe for lists containing `undefined`,
// but good enough to make the point. // but good enough to make the point.
const para = (reducer, accumulator, [x, ... xs]) => const para = (reducer, accumulator, elements) => {
x !== undefined if (elements.length === 0)
? reducer(x, xs, para(reducer, accumulator, xs)) return accumulator
: accumulator
const head = elements[0]
const tail = elements.slice(1)
return reducer(head, tail, para(reducer, accumulator, tail))
}
const suffixes = list => para( const suffixes = list => para(
(x, xs, suffxs) => [xs, ... suffxs], (x, xs, suffxs) => [xs, ... suffxs],