Hi folks, rather than discussing about which operator symbol to use for record access, which is really a question of personal taste we should try to seriously discuss the proposals and get to a solutions! We all seem to agree that records are broken in Haskell. In order to fix that we need a new and most probably incompatible solution. However, I think the new solution should go in a new version of the Haskell standard (among other things :-) ). I would strongly disadvice to try to stick with the old system and improve it. Just because there are lots of different opinions we should still try to find a reasonable solution soon. Desite the minor problem of '.' that dominated the discussion so far, what are the REAL offences against Simons proposal [1] (denoted as SR in the following)? To me it sounds like a very reasonable starting point. Which other proposals exist? I quote David Roundy's list of problems [2] with a short annotation whether SR solves them: 1. The field namespace issue. solved by not sharing the same namespace with functions 2. Multi-constructor getters, ideally as a function. not solved. only possible by hand - As stated by Wolfgang Jeltsch [3] another datatype design might be better - I can image a solution is within SR example:
data Decl = DeclType { name :: String, ... } | DeclData { name :: String, ... } | ... d :: Decl in addition to d.DeclType.name d.DeclData.name we provide (only if save, see 3.) d.name
3. "Safe" getters for multi-constructor data types. not supported as it is - with the above suggestion it could be possible (don't know if desireable) 4. Getters for multiple data types with a common field. - solved with contrains > getx :: (r <: { x :: a }) => r -> a 5. Setters as functions. doesn't seem to be supported, or I don't see it right now. 6. Anonymous records. Supported 7. Unordered records. I don' t understand it. points added from me: 8. Subtyping Supported, quite nicely 9. higher order versions for selecting, updateing ... [4] not supported seems important to me, any solutions? Regards Georg [1] http://research.microsoft.com/~simonpj/Haskell/records.html [2] http://www.haskell.org//pipermail/haskell-cafe/2005-November/012226.html [3] http://www.haskell.org//pipermail/haskell-cafe/2005-November/012227.html [4] http://www.haskell.org//pipermail/haskell-cafe/2005-November/012162.html Am Donnerstag, 17. November 2005 19:08 schrieb Dimitry Golubovsky:
Sebastian Sylvan wrote:
Personally I think that the dot is way to good of a symbol to be "wasted" on function composition. I mean, how often do you really use function composition in a way which doesn't obfuscate your code? I use ($) way more often than (.). Some people do use it more often than I
I found it useful to use (mainly for debugging purposes)
mapM (putStrLn . show) <some list>
if I want to print its elements each on a new line.
-- Dimitry Golubovsky
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