Wandering and wonderings

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| 來自：ywsing0
| 時間：Thu 2018-10-11 15:19:40
|
| 弄了一個 fluent 形式的「顯微鏡」組合子來作 immutable updates.
| 例如
| 
| let upd0 = lens().key('t').apply(t =&gt; t + 1);
| let upd1 = lens().key('vscroll').key('vms').index(3).apply(vm =&gt; Math.random().toString());
| 
| setInterval(() =&gt; renderAgain(rd_vm, upd0), 1000);
| setInterval(() =&gt; renderAgain(rd_vm, upd1), 3000);
| 
| 
| 這居然花了我大半天！
| 
| 詳情在 fun.js...
| 
| 
| let lens_ = gp =&gt; {
| 	return {
| 		apply: f =&gt; object0 =&gt; {
| 			let { g: object1, p, } = gp(object0);
| 			return p(f(object1));
| 		},
| 		index: index =&gt; lens_(object0 =&gt; {
| 			let { g: object1, p, } = gp(object0);
| 			return {
| 				g: object1[index],
| 				p: value =&gt; p([...object1.slice(0, index), value, ...object1.slice(index + 1, object1.length),]),
| 			};
| 		}),
| 		key: key =&gt; lens_(object0 =&gt; {
| 			let { g: object1, p, } = gp(object0);
| 			return {
| 				g: object1[key],
| 				p: value =&gt; p({ ...object1, [key]: value, }),
| 			};
| 		}),
| 	};
| };
| 
| let lens = () =&gt; lens_(object =&gt; ({ g: object, p: value =&gt; value, }));