Helper functions missing from Angular's Signal implementation

signal-helpers.ts

import { signal, computed } from '@angular/core'

function writable<T>(fn: () => T) {
  const c = computed(() => signal(fn()))
  const w = () => c()()
  Object.assign(w, { set: value => c().set(value) })
  return w
}
  
function derived<T>(value: T, fn: (previous: T) => T) {
  return computed(() => (value = fn(value)))
}