hs-web3's Introduction

Web3 API for Haskell

This library implements Haskell API client for popular Web3 platforms.

Install

stack install web3

Usage

{-# LANGUAGE OverloadedStrings #-}

module Main where

-- Basic imports
import           Network.Ethereum
import           Network.Web3

-- Eth API support
import qualified Network.Ethereum.Api.Eth   as Eth
import           Network.Ethereum.Api.Types

-- ENS support
import qualified Network.Ethereum.Ens       as Ens

-- Lens to simple param setting
import           Lens.Micro                 ((.~))

main :: IO ()
main = do
    -- Use default provider on http://localhost:8545
    ret <- runWeb3 $ do

        -- Get address of default account
        me <- head <$> Eth.accounts

        -- Get balance of default account on latest block
        myBalance <- Eth.getBalance me Latest

        -- Get half of balance
        let halfBalance = fromWei (myBalance / 2)

        -- Use default account
        withAccount () $ do
            -- Get Ethereum address via ENS
            alice <- Ens.resolve "alice.address.on.eth"
            bob   <- Ens.resolve "bob.address.on.eth"

            -- Send transaction with value
            withParam (value .~ halfBalance) $ do

                -- Send transaction to alice account
                withParam (to .~ alice) $ send ()

                -- Send transaction to bob account
                withParam (to .~ bob) $ send ()

        -- Return sended value
        return halfBalance

    -- Web3 error handling
    case ret of
        Left e  -> error $ show e
        Right v -> print (v :: Ether)  -- Print returned value in ethers