A little F# for you
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I've been studying F# a lot recently and find it really mind-bending. Tomas Petricek, a fellow CPian, let me sneak preview his series of F# articles and they are very good. I took one of his examples and modified it a bit. The following code displays "sum = 6", but how that happens is other-worldly...check it out:
#light
let rec sum nums =
match nums with
| head::tail -> head + sum(tail)
| [] -> 0
printf "sum = %i" (sum [1; 2; 3])Weird, eh? F# is coooool. :cool:
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
So it seems we have a long way to learn it.;)
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OK, F# isn't going to be a one night stand.
More like waking up the next morning and wondering what species is laying next to you.
Software Zen:
delete this; -
It's for problems where you indicate what you want performed on every member of a list (map) or how you aggregate the contents of a list (reduce). In theory, because each of the operations is atomic (independent of the other items), in the case of the map operation, or the result of reducing the whole list is the same as reducing distinct subparts of the list then reducing the results of those suboperations, you can farm out subparts of the list to other cores to execute in parallel. Because it's implicit, the environment can scale the algorithm appropriately to the number of installed cores. Still, it's not much that a parallel foreach couldn't do. It's just we're not used to writing our programs as such discrete blobs of functionality, effectively putting half your program out-of-line. And I'm not sure that many of the programs we regularly use would benefit - your data set would have to be pretty big to overcome the cost of the inter-thread procedure calling required to get another core working on part of the problem. I'm not totally sure the MHz myth is as over as it seemed a few years ago. The 45nm generation with high-k dielectric looks like it may have solved or at least alleviated the leakage problems that caused such trouble with overheating when trying to ramp up the clock speeds. The Core 2 Duo E8500 is supposed to clock at 3.16GHz while keeping a Thermal Design Power of 65W (source[^]).
DoEvents: Generating unexpected recursion since 1991Thanks Mike. That's a very informative post. I think I'll read it again now. :)
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
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That looks like a huge advancement in clarity and code maintainability. (Where's the sarcasm icon when I need it)
cheers, Chris Maunder
CodeProject.com : C++ MVP
Chris Maunder wrote:
Where's the sarcasm icon when I need it
If you can't do anything about it, you expect us to help you find one? ;P
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
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Pete O'Hanlon wrote:
Grown bored with WPF now have you?
Argh! Don't say that!! I, too, feel that I "must remain" pidgeon-holed into WPF. But I don't want to feel trapped like that. I am a bit tired of WPF at the moment, considering that I've studied nothing else for the past two years! Plus, part of my agenda[^] is to see if/how F# and WPF can work together.
Pete O'Hanlon wrote:
No challenges left there?
Yeah right. I've only scratched the surface.
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
I'm going to be studying TIDDLY WINQS[^].
Deja View - the feeling that you've seen this post before.
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More like waking up the next morning and wondering what species is laying next to you.
Software Zen:
delete this;It's been so long since that's happened.
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Justin Perez wrote:
stop listenting to that crap
:suss: ... ... ... ...I almost didn't change it, you know...'Mmmbop' is fun! You're killing my zest for life.
"Who wants waffles? We got a new album out...it's called 10,000 Days. Buy it so I can afford waffles." -Maynard James Keenan
Ravel H. Joyce wrote:
"Who wants waffles? We got a new album out...it's called 10,000 Days. Buy it so I can afford waffles." -Maynard James Keenan
Tool is the best. Maynard is a genius.
I didn't get any requirements for the signature
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That looks like a huge advancement in clarity and code maintainability. (Where's the sarcasm icon when I need it)
cheers, Chris Maunder
CodeProject.com : C++ MVP
That is just what I was thinking. What a load of crap for code. Why not just write a function that takes a list and it sums everything in between? Sure would look cleaner. Gosh anything would look cleaner compared to that. I've seen pascal code that did more with less.
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I've been studying F# a lot recently and find it really mind-bending. Tomas Petricek, a fellow CPian, let me sneak preview his series of F# articles and they are very good. I took one of his examples and modified it a bit. The following code displays "sum = 6", but how that happens is other-worldly...check it out:
#light
let rec sum nums =
match nums with
| head::tail -> head + sum(tail)
| [] -> 0
printf "sum = %i" (sum [1; 2; 3])Weird, eh? F# is coooool. :cool:
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
Wow... The F# code just gave me a lisp flashback (car (cdr (cons ... ))))))))) :wtf: Functional but unreadable. Don't worry though, I'm better now.
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Thats simply a map/reduce pattern, also called folding. Here is a Scheme example:
(define (fold func accum lst)
(if (null? lst)
accum
(fold func (func accum (car lst)) (cdr lst))))(define (sum . lst) (fold + 0 lst))
(display "sum = ")
(display (sum 1 2 3)) ; prints 6 (0 + 1 + 2 + 3)
(newline)(define (product . lst) (fold * 1 lst))
(display "product = ")
(display (product 1 2 3)) ; prints 6 (1 * 1 * 2 * 3)xacc.ide
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach."Wow. That takes me back. Haven't seen that stuff since college.
"If you think of yourselves as helpless and ineffectual, it is certain that you will create a despotic government to be your master. The wise despot, therefore, maintains among his subjects a popular sense that they are helpless and ineffectual." - Frank Herbert
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That looks like a huge advancement in clarity and code maintainability. (Where's the sarcasm icon when I need it)
cheers, Chris Maunder
CodeProject.com : C++ MVP
(Where's the sarcasm icon when I need it) This is all we got to work with: :rolleyes:
Christianity: The belief that a cosmic Jewish zombie who was his own father can make you live forever if you symbolically eat his flesh and telepathically tell him you accept him as your master, so he can remove and evil force from your soul that is present in humanity because a rib-woman was convinced by a talking snake to eat from a magical tree... yeah, makes perfect sense.
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It's been so long since that's happened.
Brady Kelly wrote:
It's been so long since that's happened.
What are we talkin', days? weeks?
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
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Steve Echols wrote:
Whoa!
My sentiments exactly! The hardest part about learning F#, for me, is the fact that it has both new syntax and new concepts (well, new for me anyways). I must say, though, that I haven't had this much geeky fun in a long time! There's nothing better than freeing your mind a little bit, and thinking about things from a totally different perspective. :-D
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
It's vaguely familiar, though... Prolog, maybe?
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Brady Kelly wrote:
It's been so long since that's happened.
What are we talkin', days? weeks?
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
I exagerate, but just the other night I woke up with my face in a chapter on the ASP.NET 2.0 request handling chain.
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Rama Krishna Vavilala wrote:
of WPF or F#?
I meant WPF. I don't even know where the surface of F# is yet! :)
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
You are being very modest.:) Was it because I mentioned Karen contacted you for WPF in Action review or where you in the game before.:)
Co-Author ASP.NET AJAX in Action
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You are being very modest.:) Was it because I mentioned Karen contacted you for WPF in Action review or where you in the game before.:)
Co-Author ASP.NET AJAX in Action
Rama Krishna Vavilala wrote:
Was it because I mentioned Karen contacted you for WPF in Action review or where you in the game before.
Oh, was it you who got them in touch with me? Thanks a lot! :-D
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
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I've been studying F# a lot recently and find it really mind-bending. Tomas Petricek, a fellow CPian, let me sneak preview his series of F# articles and they are very good. I took one of his examples and modified it a bit. The following code displays "sum = 6", but how that happens is other-worldly...check it out:
#light
let rec sum nums =
match nums with
| head::tail -> head + sum(tail)
| [] -> 0
printf "sum = %i" (sum [1; 2; 3])Weird, eh? F# is coooool. :cool:
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
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Huh, I hope that this code is being written automatically by dragging Sum and Numbers controls from toolbox and dropping them on a page:) Moreover, 5th line looks like a smiley |[]->0 .
sacoskun wrote:
Huh, I hope that this code is being written automatically by dragging Sum and Numbers controls from toolbox and dropping them on a page
Yeah, and that little dog in the Windows Explorer Search screen barks at you while you drag stuff around. :rolleyes:
sacoskun wrote:
Moreover, 5th line looks like a smiley |[]->0
Wow, good catch!!
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
-
I've been studying F# a lot recently and find it really mind-bending. Tomas Petricek, a fellow CPian, let me sneak preview his series of F# articles and they are very good. I took one of his examples and modified it a bit. The following code displays "sum = 6", but how that happens is other-worldly...check it out:
#light
let rec sum nums =
match nums with
| head::tail -> head + sum(tail)
| [] -> 0
printf "sum = %i" (sum [1; 2; 3])Weird, eh? F# is coooool. :cool:
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.
Cool - your next task is to learn a) how to apply implicitly recursive functions like
foldandmaprather than explicit recursion, and b) recognise when they can be applied. To use your example, except using Haskell, 'cause that's what I like: Explicit recursion:sum [] = 0 sum (head:tail) = head + (sum tail)Differences from F# - recursion and pattern matching don't need to be explicitly stated. Oh, and if you ask Haskell what the type of
sumis, it'll reply with(Num t) => [t] -> t- basically saying thatsumis now defined for lists of any numeric type...polymorphism at work - uber cool! Implicit recursion:sum = foldl (+) 0A fold combines all elements of a collection using some function - so
sumcombines all elements of a list using the + operator (Haskell lets you use operator as functions if you surround them with brackets) starting with the accumulating value set to zero. Oh - and even though I've not defined any parameters to this sum definition, it does take one -sumis defined as a partial application offoldl, so it's equivalent tosum nums = foldl (+) 0 nums. Oh - and this definition ofsumis defined over all numeric lists as well :-) - the type offoldlis(a -> b -> a) -> a -> [b] -> a-aandbare arbitrary types,(+)has type(Num a) => a -> a -> aand0has type(Num t) => t. Combine those types all together and you get the same as the first definition ofsum! OK - I'm an FP language dweeb, I'll admit it... -
Cool - your next task is to learn a) how to apply implicitly recursive functions like
foldandmaprather than explicit recursion, and b) recognise when they can be applied. To use your example, except using Haskell, 'cause that's what I like: Explicit recursion:sum [] = 0 sum (head:tail) = head + (sum tail)Differences from F# - recursion and pattern matching don't need to be explicitly stated. Oh, and if you ask Haskell what the type of
sumis, it'll reply with(Num t) => [t] -> t- basically saying thatsumis now defined for lists of any numeric type...polymorphism at work - uber cool! Implicit recursion:sum = foldl (+) 0A fold combines all elements of a collection using some function - so
sumcombines all elements of a list using the + operator (Haskell lets you use operator as functions if you surround them with brackets) starting with the accumulating value set to zero. Oh - and even though I've not defined any parameters to this sum definition, it does take one -sumis defined as a partial application offoldl, so it's equivalent tosum nums = foldl (+) 0 nums. Oh - and this definition ofsumis defined over all numeric lists as well :-) - the type offoldlis(a -> b -> a) -> a -> [b] -> a-aandbare arbitrary types,(+)has type(Num a) => a -> a -> aand0has type(Num t) => t. Combine those types all together and you get the same as the first definition ofsum! OK - I'm an FP language dweeb, I'll admit it...Stuart Dootson wrote:
OK - I'm an FP language dweeb, I'll admit it...
Wow, but you're one knowledgable FP language dweeb! Thanks for sharing that with me. I'll have to study what you wrote, to make sure it sticks.
:josh: My WPF Blog[^] Without a strive for perfection I would be terribly bored.