hardvain

libraryDependencies += "com.chuusai" % "shapeless_2.11" % "2.3.2"

hardvain

val list1 : List[Int] = List(1,2,3) // list of integers
val list2 : List[String] = List("a","b", "c") // list of strings
val list3 : List[Any] = List(1,2,"a","b") // list of any. Here Any is the least upper bound of sting & int

hardvain

import shapeless._
val hlist1a = HList(1,2,3)
val hlist2a = HList(1,"a",3.14)
// The above code with type ascription
val hlist1b: ::[Int, ::[Int, ::[Int, HNil]]] = HList(1,2,3)
val hlist2b: ::[Int, ::[String, ::[Double, HNil]]] = HList(1,"a",3.15)

hardvain

val l = 1 :: "hello" :: true :: HNil
// l: shapeless.::[Int,shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]]] = 1 :: hello :: true :: HNil

l.head
// res7: Int = 1

l.tail
// res8: shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]] = hello :: true :: HNil

l(1)

hardvain

module IParsec 

interface Source a where
  feed : Nat -> a -> (List Char, a)
  next : a -> (List Char, a)
  next = feed 1

Source String where
  feed x string = let (first, second) = splitAt x $ unpack string in 
    (first, pack second)

hardvain

import Text.ParserCombinators.Parsec
import Data.List

type Args = [String]
type Body = [String]
type Label = String

data JSONProp = JSONProp Label JSON deriving Show
data JSON = JSONObject [JSONProp] 
          | JSONNumber Double 

hardvain

{- 
    Zachary Weaver <[email protected]>
    JSONParser.hs
    Version 0.1.1
    
    A simple example of parsing JSON with Parsec in haskell.  Note that 
    since the primary point of this excersize is demonstration, 
    Text.Parsec.Token was avoided to expose more of the grammar.  Also,
    complicated optimizations and shorcuts were avoided (mostly).

hardvain

use std::fmt::*;

/// A struct that represents a single node in a list
///
/// # State
/// * `element` - The element of type T that is stored in the node
/// * `next` - An optional value that points to the next element in the list
#[derive(PartialEq, Debug)]
pub struct Node<T: Debug> {
  pub element: T,

hardvain

 • Couldn't match type ‘Circle’ with ‘Line’
      Expected type: Tree Line
        Actual type: Tree Circle
    • In the expression: Node (Circle (20, 30) 50) []
      In the second argument of ‘Node’, namely
        ‘[Node (Circle (20, 30) 50) []]’
      In the expression:
        Node (Line (100, 100) (30, 60)) [Node (Circle (20, 30) 50) []]
   |
11 | sampleTree = Node (Line (100,100) (30,60)) [Node (Circle (20,30) 50) []]

hardvain

{-# LANGUAGE ExistentialQuantification, GADTs #-}
module Main where


class SvgNode a where
  toSVG :: a -> String
  
data SvgNodeObject where
  Pack :: SvgNode a => a -> SvgNodeObject