On Thursday 18 October 2007 10:52:26 Tom wrote:
> Not long ago I was searching the Internet on the topic "combining eager and
> lazy evaluation", and have run over a paper which I obviously dismissed as
> "not interesting enough", yet now I have realized that it could indeed be
> useful, but am unable to find it.
>
> I know it was talking about a useful primitive, I do not know how exactly
> it was named, which checked whether values passed as arguments to functions
> were lazy (blocks to be evaluated) or eager (already evaluated), and using
> it some functions, e.g. map (this example was present in the paper) could
> be implemented to be both eager and lazy at the same time, depending on the
> arguments.
>
> Does anyone recognize this description?

Scala can do something similar by controlling evaluation simply by altering 
the signature. However, I've reviewed Haskell recently and I think complete 
laziness is more of a hindrance than a benefit. The only think I'd like to 
see added to eager FPLs is the ability to pattern match over lazy values, 
forcing them only when necessary.

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/products/?e