print-debugger: Debug print formatting library.

[ debug, library, public-domain ] [ Propose Tags ]

Print debugging with stack trace for Haskell (formatted for ease of use). See screenshot:

[Skip to Readme]


Maintainer's Corner

Package maintainers

For package maintainers and hackage trustees


Versions [RSS] 0.0, 1.0.0, 1.0.1, 1.1.1, 1.1.2, 1.1.3, 1.1.4, 1.1.5, 1.1.6, 1.1.7, 1.1.8, 1.1.9
Dependencies base (<4.10), split [details]
License LicenseRef-PublicDomain
Author John-Michael Reed
Category Debug
Home page
Bug tracker
Source repo head: git clone
Uploaded by johnreedlol at 2016-02-14T22:47:35Z
Reverse Dependencies 1 direct, 0 indirect [details]
Downloads 6198 total (26 in the last 30 days)
Rating (no votes yet) [estimated by Bayesian average]
Your Rating
  • λ
  • λ
  • λ
Status Docs available [build log]
Last success reported on 2016-02-14 [all 1 reports]

Readme for print-debugger-1.1.9

[back to package description]


Prints lines with IDE friendly stack traces in Haskell (now with IDE friendly fatal assertions).


debugTraceIO "foobar"

foobar in thread "1" :


See screenshot:


  • None (except for "split" package in .cabal). Automatically imports on "cabal install print-debugger".


  1. Add the file "StackTraceDebug.hs" to your Haskell project.
  2. Add "import StackTraceDebug" if you want to call the function
  3. Call "debugTraceIO" with any String argument.
  4. When you are done, remove or comment out all calls to debugTraceIO.
  5. Optionally, set value "debugMode" to "False" in "StackTraceDebug.hs" to mute all calls to "debugTraceIO" and disable all fatal assertions.


  • Does not require to be compiled with "-prof"
  • Easier to locate your print statements (and assertions)- Location of print statement (and assertions) can be highlighted in an IDE
  • Easy to turn print statemments (and assertions) on/off without having to manually uncomment each one.
  • CC0 (Free to use, share, or modify, even commercially)


  • GHC 7.10.1 (or greater)
  • "-XImplicitParams" compiler option
  • "split" package or addition of ", split" to "build-depends" line in ".cabal" file


Sample ".cabal" file:

name: HaskellProject1

version: 1.0

Build-Type: Simple

cabal-version: >= 1.2

executable HaskellProject1

main-is: Main.hs

hs-source-dirs: src

build-depends: base, split

Sample compilation:

    $> ghc StackTraceDebug.hs -Wall -Werror -XImplicitParams

Know bugs:

^ Doesn't build correctly on Caball Ubuntu 14.04 with old (ubuntu LTS repo) version of GHC.

(but compiles fine on Windows with "ghc StackTraceDebug.hs -Wall -Werror -XImplicitParams")

To report or pinpoint bugs, email

More info: