Quickstart (5-Minute Guide)

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Control.Monad.Except (runExceptT)
import qualified Data.Text.IO as TIO
import Langchain.Prelude

main :: IO ()
main = do
  -- 1. Initialize the ChatModel instance
  model <- newOllama "qwen2.5:7b" defaultConfig

  -- 2. Construct messages
  let messages =
        [ systemMessage "You are a concise, helpful Haskell tutor."
        , userMessage "What is the difference between Functor, Applicative, and Monad?"
        ]

  -- 3. Invoke the model
  res <- runExceptT $ invoke model messages Nothing
  case res of
    Left err -> putStrLn ("Invocation Error: " ++ show err)
    Right responseMsg -> do
      putStrLn "--- LLM Response ---"
      TIO.putStrLn (extractMessageText responseMsg)

-- OpenAI
import Langchain.Provider.OpenAI

let model = newOpenAI "sk-..." "gpt-4o"

-- Google Gemini
import Langchain.Provider.Gemini

let model = newGemini "AIza..." "gemini-1.5-pro"

import Langchain.Prelude

streamExample :: IO ()
streamExample = do
  model <- newOllama "qwen2.5:7b" defaultConfig
  let messages = [userMessage "Count from 1 to 10 with explanations."]

  -- Stream tokens directly to stdout as they arrive
  streamModel model messages $ \event ->
    case event of
      LLMStart -> putStrLn "[Stream Started]"
      LLMChunk chunkText -> putStr (show chunkText)
      LLMEnd usage -> putStrLn "\n[Stream Finished]"
      _ -> pure ()

pipeline :: RunnableTree IO Text Text
pipeline =
      runLambda (\q -> "Answer in 1 sentence: " <> q)
  |>> invokeLLM model
  |>> runLambda extractMessageText

runIt :: IO ()
runIt = do
  answer <- interpret pipeline "Why is Haskell great for AI?"
  putStrLn (show answer)