Re: [Haskell] Views in Haskell

On Wednesday, January 24, 2007 10:02 AM, Dinko Tenev wrote:

On 1/24/07, Brian Hulley wrote:

...

A possible syntax could represent the value being matched explicitly, say using ? to represent the value currently being matched, then the pattern could be written as an equation:

f (prodSize ? = Small) = ... f (prodSize ? = Medium) = ... f (prodSize ? = Big) = ...

...or maybe (Small = prodSize ?), etc., to be consistent with let bindings?

I like it! Just to fix a minor error in one of my previous examples, and to show it in let-compatible form: -- "n+3" pattern matching against 2nd element j (_ : (n = ? - 3) : _ = toList ?) = ... Also, perhaps the "binding" could be optional for "True = ", so that: test (True = isAlpha ?) = ... could just be written as: test (isAlpha ?) = ... (The presence of '?' in the pattern is enough to specify that it's an "active" pattern) Here is another example, in current syntax and in "new" syntax: old (n + 3) | 0 < n = ... -- using idiosyncratic n+k pattern new (n = ? - 3) | 0 < n = ... -- rational reconstruction or new (n @ (0 < ?) = ? - 3) = ... -- moving guard into pattern Brian. -- http://www.metamilk.com