[EMAIL PROTECTED] wrote:
And what alternatives (besides call by name without sharing) are there?
http://doi.acm.org/10.1145/944705.944731
http://doi.acm.org/10.1145/581690.581694
I always think lazy evaluation is space and time optimal.
Google for optimal reduction (Lamping, Asperti,
No, I wasn't suggesting that evaluate can tell the difference, just
that you can add dubious functions.
You can evaluate with eager evaluation and some kind of threads+fair
scheduler. Both pH and the (short lived) Eager Haskell version of
ghc did this. (Well, I'm not sure pH ever got the
Sorry, it is of course Jan-Willem's compiler that is called Eager
Haskell, the Ghc version was called optimistic Haskell.
There's also the old precursor to these, the Optimistic G-machine,
that performs some non-lazy computations. (And it can even do them
while garbage collecting!)
On Sep 14, 2006, at 16:20 , [EMAIL PROTECTED] wrote:
Michael Shulman wrote:
On 9/13/06, [EMAIL PROTECTED] [EMAIL PROTECTED]
wrote:
So `seq` forces its first argument. When we define
f x = x `seq` (Return x)
we thereby get
f _|_== _|_
f [] == Return []
f (x:xs) == Return
On 9/14/06, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
With this in mind the equations
1) return _|_ == Return _|_
2) _|_ `seq` (return _|_) == _|_
can be interpreted:
1) when reducing a return-redex (i.e. evaluating it), we get weak-head
normal form without evaluating the argument
Michael Shulman wrote:
On 9/11/06, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
* (a `seq` return a) = evaluate a *right now*, then produce an IO
action
which, when executed, returns the result of evaluating a. Thus, if
a is undefined, throws an exception right now.
is a bit misleading
On 9/13/06, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
So `seq` forces its first argument. When we define
f x = x `seq` (Return x)
we thereby get
f _|_== _|_
f [] == Return []
f (x:xs) == Return (x:xs)
To compare, the semantics of (evaluate) is
evaluate _|_== ThrowException
Hello Michael,
you are correct. Only
* (a `seq` return a) = evaluate a *right now*, then produce an IO action
which, when executed, returns the result of evaluating a. Thus, if
a is undefined, throws an exception right now.
is a bit misleading as there is no evaluation right now. It's
Michael Shulman wrote:
The GHC documentation says that (evaluate a) is not the same as (a
`seq` return a). Can someone explain the difference to me, or point
me to a place where it is explained?
(evaluate a) is weaker than (a `seq` return a). (a `seq` return a) is
always _|_ whereas (evaluate
On 9/10/06, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
The GHC documentation says that (evaluate a) is not the same as (a
`seq` return a). Can someone explain the difference to me, or point
me to a place where it is explained?
(evaluate a) is weaker than (a `seq` return a). (a `seq` return
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