The hat package

[ Tags: development, library, program ] [ Propose Tags ]

hat-trans transforms Module.hs into Hat/Module.hs such that when the program is executed, a trace file Programname.hat is generated. Various tools (hat-trail, hat-observe, hat-explore ...) then allow viewing the trace file in different ways, to locate a bug or understand how a program works.

Hat 2.9 uses the haskell-src-exts parser and other Hackage libraries to reduce its own size and simplify extensions. Module imports and exports have also been improved to handle nearly all kinds of renaming, hiding, etc.

Hat 2.9 works only with ghc for Haskell 98 (plus a few extensions) and the standard Haskell 98 libraries plus some Haskell 2010 libraries. Although it should build on any operating system, most viewing tools use ASCII console escape sequences and they open xterms; hence they will only work well under Unix and X11. Tested on MacOS X 10.9.5.


cabal -v install

Flag -v allows you to see what is going on. Building takes a long time (one module has 25.000 lines of code). Don't worry about numerous warning messages. The tracing transformation does produce code with lots of overlapping patterns.


hat-make MyProgram.hs

transforms and compiles all modules of your program and produces the tracing version Hat/MyProgram.

Run your program


which will produce trace files MyProgram.hat*

Use the viewing tools to explore the trace:

hat-trail / hat-observe / hat-explore /...   MyProgram

There is documentation in the "docs" folder, but it is partially outdated. There are a few small programs for exploring tracing in the "examples" folder.


Dependencies base (>=4.5 && <5), bytestring (>=0.9), containers (>=0.5.2), directory (>=1.1), filepath (>=1.3), haskeline (>=0.6), haskell-src-exts (==1.16.*), old-locale (>=1.0), old-time (>=1.1), polyparse (>=1.11), process (>=1.1), random (>=1.0) [details]
License OtherLicense
Copyright (c) 2000-2015 Hat team
Author Hat team
Category Development
Home page
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Source repository head: git clone git://
Uploaded Thu Jul 16 15:38:06 UTC 2015 by OlafChitil
Updated Sun Aug 21 11:02:45 UTC 2016 by HerbertValerioRiedel to revision 1
Distributions NixOS:
Executables hat-make, hat-delta, pretty-hat, hat-anim, hat-nonterm, black-hat, hat-cover, hat-view, hat-check, hat-detect, hat-explore, hat-stack, hat-observe, hat-trail, hat-trans
Downloads 3564 total (19 in the last 30 days)
Rating 0.0 (0 ratings) [clear rating]
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Status Docs available [build log]
Last success reported on 2015-07-16 [all 1 reports]
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