[Functional Programming Monad] Map And Evaluate State With A
We explore our first stateful transaction,by devising a means to echo our state value into the resultant for independent modification. With our state value in the resultant,we explore using? In our exploration we find that not only can we change values of the resultant,but we can change the type as needed. We also find that we can combine subsequent map calls into function compositions,allowing us to clean up our code and combine our mappings to avoid excessive interactions with our? To wrap it all up,we take a look at a handy? ? const { curry,compose,Pair,State,mapProps,composeK } = require("crocks"); const { get } = State; // State s a // We define State as a fixed type of state ‘s‘ or the left and a variable ‘a‘ on the right // (s -> (a,s)) // State Unit defined as Pair(a,s) with ‘a‘ variable on the left and ‘s‘ on the right // add :: Number -> Number -> Number const add = x => y => x + y; // pluralize :: (String,String) -> Number -> String const pluralize = (single,plural) => num => `${num} ${Math.abs(num) === 1 ? single : plural}`; // getState :: () -> State s const getState = () => State(s => Pair(s,s)) // makeAwesome :: Number -> String const makeAwesome = pluralize(‘Awesome‘,‘Awesomes‘) // flow :: Number -> String const flow = compose( makeAwesome,add(10) ) console.log( getState() .map(flow) .runWith(2) .fst() ) ? Get state constructor is so common,there is well made function call ‘get‘ to replace our ‘getState‘: const { curry,plural) => num => `${num} ${Math.abs(num) === 1 ? single : plural}`; // makeAwesome :: Number -> String const makeAwesome = pluralize(‘Awesome‘,add(10) ) console.log( get() .map(flow) .runWith(2) .fst() ) (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |