[PureScript] Introduce to PureScript Specify Function Arguments

JavaScript does its error-checking at runtime, but PureScript has a compiler, which makes sure that your program has no errors before it converts it all into JavaScript.

PureScript's compiler uses a type system to catch errors so that you aren’t accidentally mismatching your types. We will learn the very basics of type declarations, how they work in a statically typed language like PureScript, and see simple examples of them in action.

Join in by going to PureScripts online editor

 

Define a variable type:

myTypes :: Int
myTypes = 1

 

Define a function:

add :: Int -> Int -> Int // Take a Int, another Int, return value is also Int
add a b = a + b

 

We can also define the function like that:

add = \a -> \b -> a + b

 

We can also define curry function:

-- inc (a -> (add 1 a))
inc :: Int -> Int
inc = add 1

main = render =<< withConsole do
  log $ show $ inc 5

 

Full code: 

module Main where

import Prelude
import Control.Monad.Eff.Console (log)
import TryPureScript

myTypes :: Int
myTypes = 1

-- add (a -> (b -> (a + b)))
add :: Int -> Int -> Int
add a b = a + b
addMe = \a -> \b -> a + b

-- inc (a -> (add 1 a))
inc :: Int -> Int
inc = add 1

main = render =<< withConsole do
  log $ show $ inc 5 // 6