sjmyuan

## fp-ts-technical-overview.md

      
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                gcanti
                / fp-ts-technical-overview.md
            
            
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                fp-ts technical overview
              
          
    Technical overview

A basic Option type

// Option.ts

// definition
export class None {
  readonly tag: 'None' = 'None'

  
## Alacarte.scala
object Alacarte {
  trait Functor[F[_]]{
    def map[A, B](fa: F[A])(f: A => B): F[B]
  }

  trait Eval[F[_]] {
    def F: Functor[F]

    def evalAlgebra(fa: F[Int]): Int
  }

## type-bounds.scala
class A
class A2 extends A
class B

trait M[X]

//
// Upper Type Bound
//
def upperTypeBound[AA <: A](x: AA): A = x
	object Alacarte {
	trait Functor[F[_]]{
	def map[A, B](fa: F[A])(f: A => B): F[B]
	}

	trait Eval[F[_]] {
	def F: Functor[F]

	def evalAlgebra(fa: F[Int]): Int
	}
	class A
	class A2 extends A
	class B

	trait M[X]

	//
	// Upper Type Bound
	//
	def upperTypeBound[AA <: A](x: AA): A = x