It's already under 80 chars, but I'd still love to remove the
definition of the array a, and do the whole thing with no semicolons.
Any suggestions?
If you're interested, here's an indented/commented copy that might
save a few minutes..
# create an array of integers, 2 to 100
a=(2..100).to_a;
p a.each{ |c|
# for each element c in that array, if c isn't nil, it's prime. so
set multiples of c to nil
a.map!{ |d|
c && d && c<d && d%c == 0 ? nil : d
}
}.compact # finally, print the array minus the nils
..swapped to reject, and now I don't have to test for c and d being
nil, or do the final compact. Seems ok even though I'm editing the
array I'm looping through..
;D
···
On 8/2/06, Daniel Baird <danielbaird@gmail.com> wrote:
Hi all,
I've been golfing around with the sieve of Eratosthenes. Here's what
I've got so far:
I got rid of the semi-colons and assigning the arrays (although
technically it's still 'assigned' in the inject) although it might has
made it a bit loner.
Farrel
···
On 02/08/06, Daniel Baird <danielbaird@gmail.com> wrote:
Hi all,
I've been golfing around with the sieve of Eratosthenes. Here's what
I've got so far:
It's already under 80 chars, but I'd still love to remove the
definition of the array a, and do the whole thing with no semicolons.
Any suggestions?
If you're interested, here's an indented/commented copy that might
save a few minutes..
# create an array of integers, 2 to 100
a=(2..100).to_a;
p a.each{ |c|
# for each element c in that array, if c isn't nil, it's prime. so
set multiples of c to nil
a.map!{ |d|
c && d && c<d && d%c == 0 ? nil : d
}
}.compact # finally, print the array minus the nils
Gah! Excuse my atrocious spelling and grammar. "...although it has
made it a bit longer".
···
On 02/08/06, Farrel Lifson <farrel.lifson@gmail.com> wrote:
On 02/08/06, Daniel Baird <danielbaird@gmail.com> wrote:
> Hi all,
>
> I've been golfing around with the sieve of Eratosthenes. Here's what
> I've got so far:
>
> a=(2..100).to_a;p a.each{|c|a.map!{|d|c&&d&&c<d&&d%c==0?nil:d}}.compact
>
> It's already under 80 chars, but I'd still love to remove the
> definition of the array a, and do the whole thing with no semicolons.
> Any suggestions?
>
> If you're interested, here's an indented/commented copy that might
> save a few minutes..
>
> # create an array of integers, 2 to 100
> a=(2..100).to_a;
> p a.each{ |c|
> # for each element c in that array, if c isn't nil, it's prime. so
> set multiples of c to nil
> a.map!{ |d|
> c && d && c<d && d%c == 0 ? nil : d
> }
> }.compact # finally, print the array minus the nils
>
> I'd appreciate any comments.
>
> Cheers
>
> ;Daniel
>
> --
> Daniel Baird
> http://tiddlyspot.com (free, effortless TiddlyWiki hosting)
> http://danielbaird.com (TiddlyW;nks! :: Whiteboard Koala :: Blog ::
> Things That Suck)
Here's my attempt. Note that I have made it a bit more general by
assigning s = 100 beforehand.
I got rid of the semi-colons and assigning the arrays (although
technically it's still 'assigned' in the inject) although it might has
made it a bit loner.
On 8/2/06, Daniel Baird <danielbaird@gmail.com> wrote:
> Hi all,
>
> I've been golfing around with the sieve of Eratosthenes. Here's what
> I've got so far:
>
> a=(2..100).to_a;p a.each{|c|a.map!{|d|c&&d&&c<d&&d%c==0?nil:d}}.compact
>
> It's already under 80 chars, but I'd still love to remove the
> definition of the array a, and do the whole thing with no semicolons.
> Any suggestions?
>
.swapped to reject, and now I don't have to test for c and d being
nil, or do the final compact. Seems ok even though I'm editing the
array I'm looping through..
p (2..100).inject(){|a,n|a.any?{|i|n%i==0}?a:a<<n}
> Hi all,
>
> I've been golfing around with the sieve of Eratosthenes. Here's what
> I've got so far:
>
> a=(2..100).to_a;p a.each{|c|a.map!{|d|c&&d&&c<d&&d%c==0?nil:d}}.compact
>
> It's already under 80 chars, but I'd still love to remove the
> definition of the array a, and do the whole thing with no semicolons.
> Any suggestions?
>
Daniel Baird wrote:
> > Hi all,
> >
> > I've been golfing around with the sieve of Eratosthenes. Here's what
> > I've got so far:
> >
> > a=(2..100).to_a;p a.each{|c|a.map!{|d|c&&d&&c<d&&d%c==0?nil:d}}.compact
> >
> > It's already under 80 chars, but I'd still love to remove the
> > definition of the array a, and do the whole thing with no semicolons.
> > Any suggestions?
> >
>
> Improvement:
>
> a=(2..100).to_a;p a.each{|c|a.reject!{|d|c<d&&d%c==0}}
>
> .swapped to reject, and now I don't have to test for c and d being
> nil, or do the final compact. Seems ok even though I'm editing the
> array I'm looping through..
p (2..100).inject(){|a,n|a.any?{|i|n%i==0}?a:a<<n}
p (2..100).inject(){|a,n|a.any?{|i|n%i<1}?a:a<<n}
···
> On 8/2/06, Daniel Baird <danielbaird@gmail.com> wrote:
Of course, one might make a case for making that (2..99), shaving off a
byte, since we all know 100 isn't prime. We could make that 99 lower,
but there's no point if our point is golfing.
···
On Wed, Aug 02, 2006 at 06:20:05PM +0900, William James wrote:
Daniel Baird wrote:
> On 8/2/06, Daniel Baird <danielbaird@gmail.com> wrote:
> > Hi all,
> >
> > I've been golfing around with the sieve of Eratosthenes. Here's what
> > I've got so far:
> >
> > a=(2..100).to_a;p a.each{|c|a.map!{|d|c&&d&&c<d&&d%c==0?nil:d}}.compact
> >
> > It's already under 80 chars, but I'd still love to remove the
> > definition of the array a, and do the whole thing with no semicolons.
> > Any suggestions?
> >
>
> Improvement:
>
> a=(2..100).to_a;p a.each{|c|a.reject!{|d|c<d&&d%c==0}}
>
> .swapped to reject, and now I don't have to test for c and d being
> nil, or do the final compact. Seems ok even though I'm editing the
> array I'm looping through..
p (2..100).inject(){|a,n|a.any?{|i|n%i==0}?a:a<<n}
--
CCD CopyWrite Chad Perrin [ http://ccd.apotheon.org ]
"A script is what you give the actors. A program
is what you give the audience." - Larry Wall
While that's an elegant looking solution it is not a 'true' sieve. It
builds up the primes array rather than eliminating non-primes from an
existing array.It's seems to be quite a bit slower:
require 'benchmark'
def build(max)
(2..max).inject(){|a,n|a.any?{|i|n%i<1}?a:a<<n}
end
def sieve(max)
[*2..max**0.5].inject([*2..max]){|a,c|a.reject!{|d|d!=c&&d%c==0};a}
end
Benchmark.bm do |benchmark|
benchmark.report("Build:"){build(ARGV[0].to_i)}
benchmark.report("Sieve:"){sieve(ARGV[0].to_i)}
end
C:\Documents and Settings\flifson\My Documents>ruby primes.rb 1000
user system total real
Build: 0.047000 0.000000 0.047000 ( 0.047000)
Sieve: 0.016000 0.000000 0.016000 ( 0.015000)
C:\Documents and Settings\flifson\My Documents>ruby primes.rb 10000
user system total real
Build: 1.672000 0.000000 1.672000 ( 1.688000)
Sieve: 0.359000 0.000000 0.359000 ( 0.359000)
C:\Documents and Settings\flifson\My Documents>ruby primes.rb 100000
user system total real
Build: 96.437000 0.000000 96.437000 (102.107000)
Sieve: 8.547000 0.015000 8.562000 ( 8.656000)
Farrel
···
On 02/08/06, William James <w_a_x_man@yahoo.com> wrote:
William James wrote:
> Daniel Baird wrote:
> > On 8/2/06, Daniel Baird <danielbaird@gmail.com> wrote:
> > > Hi all,
> > >
> > > I've been golfing around with the sieve of Eratosthenes. Here's what
> > > I've got so far:
> > >
> > > a=(2..100).to_a;p a.each{|c|a.map!{|d|c&&d&&c<d&&d%c==0?nil:d}}.compact
> > >
> > > It's already under 80 chars, but I'd still love to remove the
> > > definition of the array a, and do the whole thing with no semicolons.
> > > Any suggestions?
> > >
> >
> > Improvement:
> >
> > a=(2..100).to_a;p a.each{|c|a.reject!{|d|c<d&&d%c==0}}
> >
> > .swapped to reject, and now I don't have to test for c and d being
> > nil, or do the final compact. Seems ok even though I'm editing the
> > array I'm looping through..
>
> p (2..100).inject(){|a,n|a.any?{|i|n%i==0}?a:a<<n}
p (2..100).inject(){|a,n|a.any?{|i|n%i<1}?a:a<<n}
1) I don't think there's a builtin function for that, so you'll have
to create your own.
You'll probably want to add it to the Array class.
class Array
def stddev
# your function here
end
end
You could also check rubyforge.org, maybe there's a statistics library
available there.
2) Math.log
···
On 8/2/06, Wang Austin-W22255 <xuwang@motorola.com> wrote:
Hi Ruby Gurus,
Could you please point me how to do some scientific calculation in Ruby:
1) How to calculate std.dev for an integer array?
2) Is there a log() function in Ruby?
While that's an elegant looking solution it is not a 'true' sieve. It
builds up the primes array rather than eliminating non-primes from an
existing array.It's seems to be quite a bit slower:
Well thank you, I forgot about the sieve, so there is no credit to be taken
for that.
But I am not sure to understand, by using (2..100) at the beginning I have
the numbers, or is it kind of a generator which violates the rules? Anyway
we could just do the same on
[*2..100] where they are *really* there the numbers.
Using Paul's improvement, ty Paul, we would have
p [*2..100].reject{|d|(2..d-1).find{|c|d%c==0}}
which should qualify, no?
Cheers
Robert
require 'benchmark'
···
def build(max)
(2..max).inject(){|a,n|a.any?{|i|n%i<1}?a:a<<n}
end
def sieve(max)
[*2..max**0.5
].inject([*2..max]){|a,c|a.reject!{|d|d!=c&&d%c==0};a}
end
Benchmark.bm do |benchmark|
benchmark.report("Build:"){build(ARGV[0].to_i)}
benchmark.report("Sieve:"){sieve(ARGV[0].to_i)}
end
C:\Documents and Settings\flifson\My Documents>ruby primes.rb 1000
user system total real
Build: 0.047000 0.000000 0.047000 ( 0.047000)
Sieve: 0.016000 0.000000 0.016000 ( 0.015000)
C:\Documents and Settings\flifson\My Documents>ruby primes.rb 10000
user system total real
Build: 1.672000 0.000000 1.672000 ( 1.688000)
Sieve: 0.359000 0.000000 0.359000 ( 0.359000)
C:\Documents and Settings\flifson\My Documents>ruby primes.rb 100000
user system total real
Build: 96.437000 0.000000 96.437000 (102.107000)
Sieve: 8.547000 0.015000 8.562000 ( 8.656000)
Farrel
--
Deux choses sont infinies : l'univers et la bêtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.
class Array
def sd(ar)
n = length
sum_sq = inject(0.0) {|accu, v| accu + v*v}
sum = inject(0.0) {|accu, v| accu + v}
Math.sqrt((sum_sq - sum*sum/n) / (n-1))
end
end
···
On 8/2/06, Sander Land <sander.land@gmail.com> wrote:
On 8/2/06, Wang Austin-W22255 <xuwang@motorola.com> wrote:
> Hi Ruby Gurus,
>
> Could you please point me how to do some scientific calculation in Ruby:
>
> 1) How to calculate std.dev for an integer array?
> 2) Is there a log() function in Ruby?
>
> Thank you!
> Austin
1) I don't think there's a builtin function for that, so you'll have
to create your own.
You'll probably want to add it to the Array class.
class Array
def stddev
# your function here
end
end
You could also check rubyforge.org, maybe there's a statistics library
available there.
Did I get confused with replies here? If so all my appologizes,
I will do it again
R.
···
On 8/2/06, Robert Dober <robert.dober@gmail.com> wrote:
> While that's an elegant looking solution it is not a 'true' sieve. It
> builds up the primes array rather than eliminating non-primes from an
> existing array.It's seems to be quite a bit slower:
Well thank you, I forgot about the sieve, so there is no credit to be
taken for that.
But I am not sure to understand, by using (2..100) at the beginning I have
the numbers, or is it kind of a generator which violates the rules? Anyway
we could just do the same
From: Robert Dober [mailto:robert.dober@gmail.com]
Sent: Wednesday, August 02, 2006 1:26 PM
>
> > Enumerations, all the way
> >
> > p (2..100).select{|d|!(2..d-1).find{|c|d%c==0}}
>
> You can shave a byte off:
>
> p (2..100).reject{|d|(2..d-1).find{|c|d%c==0}}
p (2..100).select{|d|(2...d).all?{|c|d%c>0}}
But it has nothing to do with Eratosthenes anymore...
cheers
Simon
···
On 8/2/06, Paul Battley <pbattley@gmail.com> wrote:
> On 02/08/06, Robert Dober <robert.dober@gmail.com> wrote:
