Re: [Haskell-cafe] Re: Overloading functions based on arguments?

On Feb 13, 2009, at 6:31 PM, Krzysztof Skrzętnicki wrote:

On Fri, Feb 13, 2009 at 22:37, John A. De Goes wrote:

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On Feb 13, 2009, at 2:11 PM, Jonathan Cast wrote:

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The compiler should fail when you tell it two mutually contradictory things, and only when you tell it two mutually contradictory things.

By definition, it's not a contradiction when the symbol is unambiguously typeable. Do you think math textbooks are filled with contradictions when they give '+' a different meaning for vectors than matrices or real numbers???

I can easily imagine a book which uses some operator in ambiguous way yet relies on readers' intelligence in solving that issue. It is OK to do that as long as it is easy. However: it can get arbitrarily worse.

Don't overlook the advantages of using familiar operators and names: you have some intuition about '+' and 'map', so if you see them, then you'll have some idea what they do (assuming the author is neither stupid nor malicious). However, if you see some operator like '$>+' or some name like 'pp3', then you probably won't have any intuition about it. Writing good software is about conveying intentions, and part of the way we can do that is relying on what other people already know. Which means using familiar names and operators when it is helpful to do so.

I would consider any book which is hard to read because of that badly written. Things are quite similar with the code.

I consider the current state of affairs quite poor: namely, abuse of type classes and alternate names and operators that aren't very suggestive, but were chosen purely to avoid conflicts.

Programming language should be easy to reason about for both computers and humans. Compiler should therefore disallow programming style that is inaccessible for potential readers. Want to overload something? Well, use typeclasses to be explicit about it.

Type classes were not designed for name overloading. They're designed to factor out common patterns in programming. You shouldn't use a type class just because you want to use a name or operator. And as I said before, if you want to "disallow programming style that is inaccessible for potential readers," then you should disallow the current state of affairs. Regards, John A. De Goes N-BRAIN, Inc. The Evolution of Collaboration http://www.n-brain.net | 877-376-2724 x 101