تركيب الدوال والمعاملات بأمان

مقدمة

التركيب الأساسي

function compose<A extends any[], B, C>(g: (b: B) => C, f: (...args: A) => B) {
  return (...args: A): C => g(f(...args))
}

function toLen(a: string, n: number) { return `${a}${n}`.length }
function isEven(x: number) { return x % 2 === 0 }

const c1 = compose(isEven, toLen)
const ok = c1("id", 99)   // boolean

مساعد pipe

function pipe<A extends any[], B, C>(f: (...args: A) => B, g: (b: B) => C) {
  return (...args: A): C => g(f(...args))
}

const p1 = pipe(toLen, isEven)
const ok2 = p1("xx", 7) // boolean

تركيب 3 دوال فأكثر

function compose3<A extends any[], B, C, D>(h: (c: C) => D, g: (b: B) => C, f: (...args: A) => B) {
  return (...args: A): D => h(g(f(...args)))
}

function toUpper(s: string) { return s.toUpperCase() }

const c3 = compose3(toUpper, (x: number) => x.toString(), toLen)
const val = c3("a", 5) // "2" → then upper → "2"

ربط معاملات البداية

function bindHead<A extends any[], B>(fn: (...args: A) => B, ...head: A) {
  return (...rest: []): B => fn(...head)
}

const bh = bindHead(toLen, "x", 42)
const r = bh() // number

نصائح

التحقق من توقيع compose

مراجعة