debug-trace-var
When writing print debug, we often write.
import Debug.Trace
main :: IO ()
main = do
let a = 1
traceIO $ "a = " ++ show a
This is troublesome to describe the name of the variable twice.
With debug-trace-var you write variables only once.
{-# LANGUAGE QuasiQuotes #-}
import Debug.Trace.Var
main :: IO ()
main = do
let a = 1
[traceVarIO|a|]
or
{-# LANGUAGE TemplateHaskell #-}
import Debug.Trace.Var
main :: IO ()
main = let a = 1 :: Int
in $(traceMTH 'a)
You may avoid name quotes that are confusing with character literals,
Or often it may be to avoid the QuasiQuotes to destroy the syntax highlight of the text editor.
Example
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}
import Debug.Trace.Var
-- > a
-- n = 1
-- s = "あ"
a :: IO ()
a = let n = 1
s = "あ"
in [traceVar|n|] ([traceVar|s|] return ())
-- > b
-- "n = 1
-- n = 1"
b :: String
b = let n = 1
in [traceVarId|n|]
-- > c
-- n = 344
c :: IO ()
c = let n = 344
in [traceStackVar|n|] (return ())
-- > d
-- n = 344
-- n = 344
d :: IO ()
d = do
let n = 344
[traceVarIO|n|]
[traceVarIO|n|]
-- > e
-- n = 344
e :: IO ()
e = do
let n = 344
[traceVarM|n|]
-- > f
-- n = 344
f :: IO ()
f = let n = 344
in $(traceMTH 'n)
Motivation
I wanted to use Template Haskell.
One point advice
You can use ndmitchell/debug: Haskell library for debugging