[JS Compose] 5. Create types with Semigroups
An introduction to concatting items via the formal Semi-group interface. Semi-groups are simply a type with a concat method that are associative. We define three semigroup instances and see them in action.
A semigroup is a type with a concat method. Let's see if we have a string A, we can concat that with the string B. String is the semigroup here because it has a concat method. If we log this out here, we shall see the results AB and there we are.
"a".concat("b").concat("c"); //"abc"
"a".concat("b".concat("c")); //"abc"
We can also define our own semi-group:
const Sum = x =>
({
x, // we need to export x, so we can access it
concat: o => Sum(o.x + x), // o -> Sum(x)
toString: () => `Sum(${x})`
}); const res = Sum().concat(Sum());
console.log(res.toString()); // Sum(3)
const All = x => ({
x,
concat: o => All(o.x && x),
toString: ()=> `All(${x})`
}); const res = All(true).concat(All(false));
console.log(res.toString()); // All(false)
const First = x => ({
x,
concat: o => First(x),
toString: () => `First(${x})`
}); const res = First(true).concat(First(false));
console.log(res.toString()); // First(true)
[JS Compose] 5. Create types with Semigroups的更多相关文章
- Node.js NPM Tutorial: Create, Publish, Extend & Manage
A module in Node.js is a logical encapsulation of code in a single unit. It's always a good programm ...
- [JS Compose] 0. Understand 'Box' or 'Container', they are just like Array!
We'll examine how to unnest function calls, capture assignment, and create a linear data flow with a ...
- [JS] Topic - Object.create vs new
故事背景 Ref: 你不知道的javascript之Object.create 和new区别 var Base = function () {} (1) var o1 = new Base(); (2 ...
- js创建对象 object.create()用法
Object.create()方法是ECMAScript 5中新增的方法,这个方法用于创建一个新对象.被创建的对象继承另一个对象的原型,在创建新对象时可以指定一些属性. 语法: Object.crea ...
- [Compose] 19. Leapfrogging types with Traversable
We use the traversable instance on List to reimplement Promise.all() type functionality. For example ...
- [JS Compose] 7. Ensure failsafe combination using monoids
monoids is a semi-group with a neutral element. A semigroup, it does not have an element to return s ...
- [JS Compose] 3. Use chain for composable error handling with nested Eithers (flatMap)
We refactor a function that uses try/catch to a single composed expression using Either. We then int ...
- [JS Compose] 2. Enforce a null check with composable code branching using Either
We define the Either type and see how it works. Then try it out to enforce a null check and branch o ...
- [JS Compose] 1. Refactor imperative code to a single composed expression using Box
After understanding how Box is, then we are going to see how to use Box to refacotr code, to un-nest ...
随机推荐
- HDU4825 Xor Sum(贪心+Trie树)
Problem Description Zeus 和 Prometheus 做了一个游戏,Prometheus 给 Zeus 一个集合,集合中包含了N个正整数,随后 Prometheus 将向 Zeu ...
- C#之菜单控件、主窗体打开子窗体、GroupBox控件使用
一.背景 一年前有学习过C#,但没有在项目中去实际做APP,重新捡起来应用到项目中.我同事本来做好一个CANOPEN设备管理的界面,由于近期搜索了别人的开发的界面,我觉得有很多东西要重新安排,以及我已 ...
- [React & Testing] Simulate Event testing
Here we want to test a toggle button component, when the button was click, state should change, styl ...
- HTML5梦幻星空,可用作网页背景
<html> <head> <title>星空</title> <META http-equiv="X-UA-Compatible&qu ...
- CentOS6 安装中文包和变更系统默认语言
CentOS6 安装中文包和变更系统默认语言 用 yum 安装语言包的命令是 yum groupinstall <language>-support ,其中 <langua ...
- FAILOVER详细步骤
FAILOVER详细步骤 1.Flush主库任何未传输的redo到目标备库 如果primary可以mount,则可以flush任何主库的未传输redo到备库,如果操作成功返回,则可以保证failove ...
- VC 常见问题百问
http://www.cnblogs.com/cy163/archive/2006/06/19/429796.html 经典Vc书 Charles Petzold 的<Programming W ...
- 00103_死锁、Lock接口、等待唤醒机制
1.死锁 (1)同步锁使用的弊端:当线程任务中出现了多个同步(多个锁)时,如果同步中嵌套了其他的同步.这时容易引发一种现象:程序出现无限等待,这种现象我们称为死锁.这种情况能避免就避免掉: synch ...
- debian 9 安装后需做的几件事
debian 9 安装后需做的几件事 安装环境:X86 >> Debian 9 Linux/GNU apt源更新 注意连上有线网络 刚安装好的debian系统中,/etc/apt/sour ...
- 微信支付v2开发(2) 微信支付账号体系
本文介绍微信支付账号体系各参数. 商户在微信公众平台提交申请资料以及银行账户资料,资料审核通过并签约后,可以获得表6-4所示帐户(包含财付通的相关支付资金账户),用于公众帐号支付. 帐号 作用 app ...