容器、Functor(函子)
函子，遵守特殊规定的容器
标志，具有map方法
//平平无奇的容器
var Container = function(x){
this.__value = x;
}
Container.of = x=> new Container(x);
Container.of('abcd');
//map方法，变形关系，把当前容器中的值可以变形到另一个容器
Container.prototype.map = function(f){
return Container.of(f(this.__value));
}
//函子
Container.of(3) //Container(3)
.map(x=>x+1) //Container(4)
.map(x=>'Result is '+x);//Container('Result is 4');
map
class Functor{
constructor(val){
this.val = val;
}
map(f){
return new Functor(f(this.val));
}
};
//Functor(4)
(new Functor(2)).map(function(two){
return two+2;
});
of
纯函数，用来生成新的容器
Functor.of = function(val){
return new Functor(val);
}
maybe函子
class Maybe extends Functor{
map(f){
return this.val?Maybe.of(f(this.val)):Maybe.of(null);
}
}
//Maybe(null)
Maybe.of(null).map(function(s){
return s.toUpperCase();
})
Either
左值是右值不存在时的默认值
右值是正常情况下使用的值
class Either extends Functor{
constructor(left,right){
this.left = left;
this.right = right;
}
map(f){
return this.right?Either.of(this.left,f(this.right)):Either.of(f(this.left),this.right);
}
}
Either.of = function(left,right){
return new Either(left,right);
}
var addOne = funcion(x){
return x+1;
}
Either.of(5,6).map(addOne); //Either(5,7)
Either.of(1,null).map(addOne); //Either(2,null)
// Either.of({address:'xxx'},currentUser.address).map(updateField);
Ap函子
class Ap extends Functor{
ap(F){
return Ap.of(this.val(F.val));
}
}
//Functor(4)
Ap.of(addTwo).ap(Functor.of(2));
IO
负责处理脏数据
