CODEWITHSUNDEEP
haskellwebserviceframeworksscotty
Antman
Antman

Reputation: 493

Scotty web service

I need to create a web service to convert between different currencies using the scotty web framework in Haskell.

The web service should respond to get requests such as /convert/15?to=usd&from=eur.

I have this code so far:

{-# LANGUAGE OverloadedStrings #-}

import Web.Scotty
import Data.Monoid (mconcat)

functionxs :: a -> Int
functionxs a = 5

main = scotty 3000 $ do
  get "/:word" $ do
    name <- param "word"
    html $ mconcat ["<h1>Hi, ", name, " what's up!</h1>"]

Thus, when you execute in the browswer: http://localhost:3000/Tony the result is: Hi, Tony, what's up!

The problem is that I don't know how to change the code in order to have '/convert/15?to=usd&from=eur.' as request and get the proper answer.

Hopefully anyone can help me.

Thanks in advance.

Edited with final solution:

{-# LANGUAGE OverloadedStrings #-}

import Web.Scotty
import Data.Monoid (mconcat)
import Data.Text.Lazy (Text, pack)

main = scotty 3000 $ do
    get "/convert/:amount" $ do
        money <- param "amount"
        to <- param "to"
        frm <- param "from"
        html $ mconcat ["<h1>The result is: ", pack (show (convert 
money to frm)),  "</h1>"]

convert :: Double -> String -> String -> Double
convert a b c = if (b=="euro" && c=="usd") 
            then (a*1.091)
            else if (b=="usd" && c=="euro")
            then (a*0.915)
            else 0

Upvotes: 0

Views: 241

Answers (1)

sumo
sumo

Reputation: 155

Looking at the docs you need to call param to get what you need.

Try this as starting point:

{-# LANGUAGE OverloadedStrings #-}

import Web.Scotty
import Data.Monoid

main = scotty 3000 $ do
  get "/convert/:amt" $ do
  amt <- param "amt"
  frm <- param "from"
  to <- param "to"
  html $ "<h1>" <> amt <>" in " <> frm <> " is " <> to <> "</h1>"

I'll leave the conversion piece for you to figure out. Using <> instead of mconcat seemed cleaner as well.

Upvotes: 2

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