Boolean control structures

bool.ts

interface Boolean {
  ifTrue<T>(fn: () => T): T | undefined
  ifFalse<T>(fn: () => T): T | undefined
}

Object.assign(Boolean.prototype, {
  ifTrue(fn: Function) {
    return this ? fn.apply(this) : undefined
  },
  ifFalse(fn: Function) {
    return this ? undefined : fn.apply(this)
  }
});

let a = 4, b = 3;

console.log(
  (a > b).ifTrue(() => a - b)
)