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function* filter(f, iter) { | |
for (const a of iter) if (f(a)) yield a; | |
} | |
function* take(limit, iter) { | |
for (const a of iter) if (limit--) yield a; | |
} | |
const head = iter => take(1, iter).next().value; |
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const log = a => console.log(a); | |
// 0. | |
// map :: Functor f => (a -> b) -> f a -> f b | |
// 1. Array.prototype.map | |
// Array r => (a -> b) -> r a -> r b | |
// [1] : r a | |
// a => a + 1 : (a -> b) |
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function *entriesLazy(obj) { | |
for (const k in obj) yield [k, obj[k]]; | |
} | |
[...entriesLazy({ a: 1, b: 2 })]; | |
// [['a', 1], ['b', 2]] | |
function *mapEntriesLazy(f, iter) { | |
for (const [k, a] of iter) yield [k, f(a)]; | |
} |
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// series | |
const posts = await getPosts(); | |
const users = await getUsers(); | |
// concurrency | |
const [posts, users] = await Promise.all([ | |
getPosts(), | |
getUsers() | |
]); |
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const isIterable = a => !!(a && a[Symbol.iterator]); | |
function *flat(iter) { | |
for (const a of iter) { | |
if (isIterable(a)) yield *a; | |
else yield a; | |
} | |
} | |
function *deepFlat(iter) { |
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function f1(max) { | |
let i = -1, total = 0; | |
while (true) { | |
let a = ++i; | |
a = a * a; | |
if (!(a < max)) break; | |
total += a; | |
} | |
return total; | |
} |
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const log = console.log; | |
const isIterable = a => !!(a && a[Symbol.iterator]); | |
function *flatten(iter) { | |
for (const a of iter) { | |
if (isIterable(a)) for (const b of a) yield b; | |
else yield a; | |
} | |
} |
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function reduce(f, acc, iter) { | |
if (arguments.length == 2) { | |
iter = acc[Symbol.iterator](); | |
acc = iter.next().value; | |
} | |
for (const a of iter) acc = f(acc, a); | |
return acc; | |
} | |
function *map(f, iter) { |
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function reduce(f, acc, iter) { | |
if (arguments.length == 2) { | |
iter = acc[Symbol.iterator](); | |
acc = iter.next().value; | |
} | |
for (const a of iter) acc = f(acc, a); | |
return acc; | |
} | |
reduce((a, b) => a + b, function*() { |
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// 선택된 모든 상품 중 할인 금액이 있는 상품의 총 수량 - pipe 이용 | |
pdts.selected.dq = pipe( | |
filter(selected), | |
filter(discount), | |
_ => pdts.total(quantity, _)); | |
console.log( pdts.selected.dq(products) ); // 5 | |
// 선택된 모든 상품 중 할인 금액이 있는 상품의 총 수량 - pipe + and 이용 | |
pdts.selected.dq = pipe( |
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