May 2003 - Libraries - Haskell.org

Advice on Library Interface
by Matthew Donadio 08 May '03

08 May '03

Hi all, One part of the DSP library that I am working on is a module for generating sequences of Gaussian random variables. Since this may be of use to people outside the DSP community, I wanted to get some suggestions on the interface. Right now, I have a few different methods for generating white gaussian noise. They all behave the same, but have different ranges and efficiencies. 1. Should the functions generate the necessary uniforms, or accept a list of uniforms? In other words, shuld the signature be wgn :: Int -- ^ seed to generate the uniforms -> [Double] -- ^ list of Gaussian random variables or wgn :: [Double] -- ^ list of uniform random variables -> [Double] -- ^ list of Gaussian random variables The first is what I currently have implemented, but the second is more flexible. 2. Should the functions accept mean and/or variance parameters, or should they generate unit normals? For those who forget X' = mean + sqrt var * X or X' = mean + stddev * X For a point of reference, the GNU scientific library function for WGN has a stddev parameter. I will probably be sending out a bunch of other emails in the next week or two. Thanks. -- Matthew Donadio (m.p.donadio(a)ieee.org)

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Seeking More Advice on Library
by Matthew Donadio 08 May '03

08 May '03

Hi all, One of the needs for a few of my DSP routines is support for functions over polynomials. The attached file is what I threw together. Since this definetly has a broader scope than just me, I wanted to get some opionions on it. 1. The module is pretty type-free right now. I wanted to get some opionions on the best type for polynomials and names for the type and constructor(s). The big question here (in my mind) is how to represent polynomials. The most obvious way is as a list of the coefficients. They can also be represented as a list of the roots. Should there be a single type with two constructors or two types each with one constructor. 2. Are there any functions that are missing? I have a root finder in a different module (the one from Numeric Quest; Laguerre's method), but I am going to rewrite it in terms of the module that I attached. Functions for inflation and deflation by a single root will need to be added. 3. Should I add infix operators? I'm not sure what to do about this because of namespace clutter. Any other thoughts? Once again, thanks. -- Matthew Donadio <m.p.donadio(a)ieee.org>

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Type of Control.Monad.Writer.listens
by Tom Pledger 05 May '03

05 May '03

Hi. Is this an appropriate place to report library bugs, or should I post to the various <implementation>-bugs lists instead? According to http://www.haskell.org/ghc/docs/latest/html/base/Control.Monad.Writer.html listens :: (MonadWriter w m) => (w -> w) -> m a -> m (a, w) but the inferred type is more general (and more useful) listens :: (MonadWriter w m) => (w -> b) -> m a -> m (a, b) Regards, Tom

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Library hierarchy.
by Axel Simon 02 May '03

02 May '03

Hi, it is quite late to complain about the hierarchy of the new hierarchical library. But I think I should do it eventually. There is a path Graphics.UI which I think is conceptually wrong. User Interfaces are not a subset of Graphics but rather the other way round. I don't know if it makes sense to do graphics without interacting with the user, if not then I would expect the hierarchy to look more like this: UI.GUI -- GUI stuff like ObjectIO or CGA UI.Graphics -- stand-alone graphics stuff like HOpenGL UI.Joystick -- An example of a non-graphical user interface I guess for compatibility, Graphics has to stay. Could we have a top-level UI branch so the CGA can go in there? Axel.

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by james＠hello.com 01 May '03

01 May '03

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