You people rock. Responses were really helpful and I understand how
the computation goes now.
I see I need to reprogram my eyes to expect lazy evaluation in places
where I am used to one-shot results. I see lazy evaluation is all
around in Haskell builtins.
From a formal point of view
Hello Xavier,
Thursday, August 23, 2007, 3:08:25 AM, you wrote:
I am learning Haskell with Programming in Haskell (an excellent
book BTW).
scheme of lazy evaluation called graph reduction
you may consider it as repetitive replacing right parts of function
definitions with their left parts.
Stefan O'Rear wrote:
As is usual for mathematical things, there are many equivalent
definitions. My two favorites are:
1. Normal order reduction
In the λ-calculus, lazy evaluation can be defined as the (unique up to
always giving the same answer) evaluation method, which, if *any*
Stefan O'Rear [EMAIL PROTECTED] writes:
Indeed, you've caught on an important technical distinction.
Lazy: Always evaluating left-outermost-first.
I think most people would rather use the term normal order¨
for that; lazy means evaluating in normal order /and/ not
evaluating the same
Hugh Perkins wrote:
On 8/22/07, Twan van Laarhoven [EMAIL PROTECTED] wrote:
But Double is already quite badly behaved:
let x = 1e20
Prelude 1 + (x - x)
1.0
Prelude (1 + x) - x
0.0
E. Whilst that's understandable and unavoidable, that kindof
rings alarm bells for folds of
I'm trying to understand lazy evaluation as well. I created an
example for myself and I'm wondering if I've got it right.
let adder n = \x - n + x in (map (adder 12) [1,2,3]) !! 1
So the first thing I did is draw a graph to represent my expression.
(map (adder 12) [1,2,3]) !! 1 =
Hi
Its (==) isn't
reflexive (is it transitive? probably, at least if there aren't too many
optimizations, but floating-point transitive equality isn't very useful).
It's not even referentially transparent in all cases. a == b may fail
while the double's are in the high precision registers,
Dave Tapley wrote:
Hi again all, I could do with some design pointers for a project I'm
working on combining Haskell with a robot.
My situation is:
I read sensor data from the robot lazily a line at a time, as soon as
a line is read in my code sends out a response down a pipe.
Implemented in
Hello All,
I've already announced this on the Gtk2Hs users' list, but for those who
are not using Gtk2Hs at the moment, but who might be interested:
I've started a port of the Gtk+2.0 tutorial by Tony Gail and Ian Main
and the first part is available on:
Hello Isaac,
Thursday, August 23, 2007, 4:17:52 PM, you wrote:
Using IORefs in two different threads probably needs MVars [1] or TVars
no documentation where it should be:
the best documentation still is
Tackling the awkward squad: monadic input/output, concurrency,
exceptions, and
Neil Mitchell wrote:
sum (enum 1 10) =
sum' 0 (enum 1 10) =
...
sum' 36 (9 : enum (9+1) 10) =
(sum' $! (36+9)) (enum (9+1) 10) =
sum' 45 (enum (9+1) 10) =
sum' 45 [] =
45
(I need to find some way to automate making these trails
apfelmus wrote:
Yeah, the precise details may vary, even :) But for teaching, an
automatic tool that does graph reduction would be great. I don't mind
if it's sloppy (directly apply definitions pattern matching VS
everything is a lambda abstraction) and only does simply typed lambda
calculus
Hi
Yeah, the precise details may vary, even :) But for teaching, an
automatic tool that does graph reduction would be great. I don't mind
if it's sloppy (directly apply definitions pattern matching VS
everything is a lambda abstraction) and only does simply typed lambda
calculus (no
Ronald Guida wrote:
Can anyone tell me if I've got this right?
Yes, you got. The let-statement you introduce that embodies the sharing
of the argument n = 12 probably should be present in the first parts,
too. But this doesn't really matter, the formalities of graph reduction
vary with the
I think DrScheme does that for Scheme. So a must have for Haskell! Maybe could
be added to the Helium project?
- Oorspronkelijk bericht -
Van: apfelmus [mailto:[EMAIL PROTECTED]
Verzonden: donderdag, augustus 23, 2007 08:00 PM
Aan: haskell-cafe@haskell.org
Onderwerp: [Haskell-cafe] Re:
First of all, I'm really excited that GTK2HS 0.9.12 now allows launching SOE
apps using GHCI.
However, in the code below the blue and green triangle should render on top of
each other, but the green triangle is rendered incorrectly.
Being a newbie, I hesitate to file a bug report... Can anyone
On 8/20/07, Stefan O'Rear [EMAIL PROTECTED] wrote:
...
(I need to find some way to automate making these trails :) )
...
I think you can come a long way with the debugger in GHC HEAD. It
provides a :trace command that, when applied to an expression with
some breakpoint in it, remembers the
On 8/23/07, Neil Mitchell [EMAIL PROTECTED] wrote:
It's not even referentially transparent in all cases. a == b may fail
while the double's are in the high precision registers, and then
succeed later on in the program once they are truncated. I think you
have to specify -fexcess-precision with
Hi,
I've been trying to find place to use Haskell at work, and I think a good
opportunity will be to use it for our scripting language. To do that, I need
to be able to invoke an interpreter directly from another language.
I've investigated using HaskellScript (too web/ActiveX centric), but
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