Structural Recursion
2022 年 10 月 3 日
Goal: Tramsform and implete algebraic data types
structure of the code follows structure of the data
We have two patterns need to follow:
- pattern matching
- polymorphism
In the First, we defined a algebraic data type
type ADType = {
type: string
}
type Email = ADType & {
host: string
address: string
}
type Address = ADType & {
country: string
address: string
}
type ConnectMethod = Email | Address
const aUser_ConnectMethod: ConnectMethod = {
type: "email",
host: "host",
address: "add"
}
const bUser_ConnectMethod: ConnectMethod = {
type: "address",
country: "country",
address: "address"
}
pattern matching
const SendNotificationToUser = (method: ConnectMethod) => {
switch(method.type){
case "email":{
console.log("the user chiose email method to notify")
break;
}
case "address":{
console.log("the user chiose address method to notify")
break;
}
}
}
SendNotificationToUser(aUser_ConnectMethod)
>>> the user chiose email method to notify
polymorphism
interface NotifyMethod {
(method: ConnectMethod): void;
}
const SendEMail: NotifyMethod = (m: Email): void => {
console.log(`the user chiose email method to notification`)
}
const SendMail: NotifyMethod = (m: Address): void =>{
console.log(`the user chiose address method to notification`)
}
SendEMail(aUser_ConnectMethod)
SendMail(bUser_ConnectMethod)
>>> the user chiose email method to notification
>>> the user chiose address method to notification
Summary
- Processing algebraic data types immediately follows from the structure of the data
- choose between pattern matching and polymorphism by your perferred