Currency.purs

module Main where

import Prelude
import Data.Tuple
import Control.Monad.Eff.Console (log)
import TryPureScript (render, withConsole)

data Currency 
  = BTC
  | USD
  
showCurrencyImpl :: Currency -> String
showCurrencyImpl BTC = "btc"
showCurrencyImpl USD = "usd"

instance showCurrency :: Show Currency where
  show = showCurrencyImpl

data CurrencyPair a b = CurrencyPair Currency Currency

showCurrencyPairImpl :: (CurrencyPair Currency Currency) -> String
showCurrencyPairImpl (CurrencyPair base quote) = 
  show base <> "-" <> show quote

instance showCurrencyPair :: Show (CurrencyPair Currency Currency) where
  show = showCurrencyPairImpl

symbol :: CurrencyPair Currency Currency
symbol = CurrencyPair BTC USD

main = render =<< withConsole do
  log $ show symbol