Hoed-0.3.0: Lighweight algorithmic debugging.

Copyright(c) 2000 Andy Gill, (c) 2010 University of Kansas, (c) 2013-2014 Maarten Faddegon
Safe HaskellNone




Hoed.Stk is a tracer and debugger for the programming language Haskell. You can trace a program by annotating functions in suspected modules and linking your program against standard profiling libraries.

Hoed.Pure is recommended over Hoed.Stk because to debug your program with Hoed.Pure you can optimize your program and do not need to enable profiling.

After running the program a computation tree is constructed and displayed in a web browser. You can freely browse this tree to get a better understanding of your program. If your program misbehaves, you can judge the computation statements in the tree as right or wrong according to your intention. When enough statements are judged the debugger tells you the location of the fault in your code.

I work on this debugger in the context of my Ph.D. research. Read more about the theory behind Hoed at http://maartenfaddegon.nl/#pub.

To use Hoed on your own program, annotate your program as described below. For best results profiling is enabled and optimization disabled. If you use cabal to build your project, this is be done with:

cabal configure --disable-optimization --enable-profiling

I am keen to hear about your experience with Hoed: where did you find it useful and where would you like to see improvement? You can send me an e-mail at hoed@maartenfaddegon.nl, or use the github issue tracker https://github.com/MaartenFaddegon/hoed/issues.


Basic annotations

observe :: Observable a => String -> a -> a Source

Functions which you suspect of misbehaving are annotated with observe and should have a cost centre set. The name of the function, the label of the cost centre and the label given to observe need to be the same.

Consider the following function:

triple x = x + x

This function is annotated as follows:

triple y = (observe "triple" (\x -> {# SCC "triple" #}  x + x)) y

To produce computation statements like:

triple 3 = 6

To observe a value its type needs to be of class Observable. We provided instances for many types already. If you have defined your own type, and want to observe a function that takes a value of this type as argument or returns a value of this type, an Observable instance can be derived as follows:

  data MyType = MyNumber Int | MyName String deriving Generic

  instance Observable MyType

runO :: IO a -> IO () Source

The main entry point; run some IO code, and debug inside it. After the IO action is completed, an algorithmic debugging session is started at http://localhost:10000/ to which you can connect with your webbrowser.

For example:

  main = runO $ do print (triple 3)
                   print (triple 2)

printO :: Show a => a -> IO () Source

Short for runO . print.

Experimental annotations

observeCC :: Observable a => String -> a -> a Source

observe' :: Observable a => String -> Identifier -> a -> (a, Int) Source

(*>>=) :: Monad m => m a -> (Identifier -> (a -> m b, Int)) -> (m b, Identifier) Source

(>>==) :: Monad m => (m a, Identifier) -> (Identifier -> (a -> m b, Int)) -> (m b, Identifier) Source

(>>=*) :: Monad m => (m a, Identifier) -> (Identifier -> (a -> m b, Int)) -> m b Source

logO :: FilePath -> IO a -> IO () Source

The Observable class

newtype Observer Source


O (forall a. Observable a => String -> a -> a) 

class Observable a where Source

Minimal complete definition



observer :: a -> Parent -> a Source

(<<) :: Observable a => ObserverM (a -> b) -> a -> ObserverM b infixl 9 Source

thunk :: (a -> Parent -> a) -> a -> ObserverM a Source

nothunk :: a -> ObserverM a Source

send :: String -> ObserverM a -> Parent -> a Source

observeBase :: Show a => a -> Parent -> a Source

observeOpaque :: String -> a -> Parent -> a Source

debugO :: IO a -> IO [Event] Source

run some code and return the CDS structure (for when you want to write your own debugger).

data CDS Source


class Generic a

Representable types of kind *. This class is derivable in GHC with the DeriveGeneric flag on.

Minimal complete definition

from, to