Here is another small Ruby code snippet that extends the Array class. Use
this to randomize the order of all entries in an Array.
class Array
def shuffle
self.each_index { |i| r = rand(self.length - 1);
self[i],self[r] = self[r],self[i] }
end
end
Works like this:
a = Array[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a.shuffle
==> [7, 10, 9, 6, 4, 8, 5, 3, 1, 2]
S.
Stefan Arentz wrote:
Here is another small Ruby code snippet that extends the Array class. Use
this to randomize the order of all entries in an Array.class Array
def shuffle
self.each_index { |i| r = rand(self.length - 1);
self[i],self[r] = self[r],self[i] }
end
endWorks like this:
a = Array[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a.shuffle
==> [7, 10, 9, 6, 4, 8, 5, 3, 1, 2]S.
This seems like a relevant discussion:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/19125
Chad
Here is another small Ruby code snippet that extends the Array class. Use
this to randomize the order of all entries in an Array.class Array
def shuffle
self.each_index { |i| r = rand(self.length - 1);
self[i],self[r] = self[r],self[i] }
end
endWorks like this:
a = Array[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a.shuffle
==> [7, 10, 9, 6, 4, 8, 5, 3, 1, 2]
ary = (0…10).to_a
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
ary.sort { rand(3)-1 }
=> [4, 6, 5, 0, 2, 3, 9, 7, 8, 1, 10]
…of course, this probably won’t produce as random as result, but it’s easier to implement.
Jason Creighton
On 08 Jul 2003 03:01:30 +0200 Stefan Arentz stefan.arentz@soze.com wrote:
rand(x) gives a number between 0 and x-1, so I think you should use
rand(self.length) not rand(self.length-1). In particular this will work
properly for arrays containing 1 element.
You could also replace self.each_index and self.length with
each_index and length, respectively. And you don’t need the semicolon.
Regards,
Brian.
On Tue, Jul 08, 2003 at 10:21:42AM +0900, Stefan Arentz wrote:
Here is another small Ruby code snippet that extends the Array class. Use
this to randomize the order of all entries in an Array.class Array
def shuffle
self.each_index { |i| r = rand(self.length - 1);
self[i],self[r] = self[r],self[i] }
end
end
“Brian Candler” B.Candler@pobox.com wrote in message
news:20030708063637.GA74975@uk.tiscali.com…
Here is another small Ruby code snippet that extends the
Array class. Use
this to randomize the order of all entries in an Array.class Array
def shuffle
self.each_index { |i| r = rand(self.length - 1);
self[i],self[r] = self[r],self[i] }
end
endrand(x) gives a number between 0 and x-1, so I think you
should use
rand(self.length) not rand(self.length-1). In particular
this will work
properly for arrays containing 1 element.You could also replace self.each_index and self.length
with
each_index and length, respectively. And you don’t need
the semicolon.Regards,
Brian.
How come when I try out this code snippet in IRB, including
entering the array, it does nothing? Am I missing
something?
Joe Gwozdecki
Houston, Texas
On Tue, Jul 08, 2003 at 10:21:42AM +0900, Stefan Arentz wrote:
I don’t know. Here’s an irb session log:
$ irb
irb(main):001:0> class Array
irb(main):002:1> def shuffle
irb(main):003:2> each_index { |i| r = rand(length)
irb(main):004:3> self[i],self[r] = self[r],self[i] }
irb(main):005:2> end
irb(main):006:1> end
=> nil
irb(main):007:0> a = [1,2,3,4,5,6,7,8,9,10]
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
irb(main):008:0> a.shuffle
=> [8, 7, 1, 4, 9, 10, 3, 2, 6, 5]
irb(main):009:0> a.shuffle
=> [7, 10, 5, 9, 8, 1, 6, 3, 4, 2]
irb(main):010:0>
What did you do differently? Note that if you miss a bracket or an ‘end’
then irb may think you are in a continuation line; if the prompt ends with
an asterisk this is a pretty strong clue.
irb(main):012:0> [
irb(main):013:1* 1,2,3
irb(main):014:1> ]
=> [1, 2, 3]
Regards,
Brian.
On Wed, Jul 09, 2003 at 06:05:28AM +0900, Joe Gwozdecki wrote:
How come when I try out this code snippet in IRB, including
entering the array, it does nothing? Am I missing
something?
“Brian Candler” B.Candler@pobox.com wrote in message
news:20030708224157.GA75351@uk.tiscali.com…
How come when I try out this code snippet in IRB,
including
entering the array, it does nothing? Am I missing
something?I don’t know. Here’s an irb session log:
$ irb
irb(main):001:0> class Array
irb(main):002:1> def shuffle
irb(main):003:2> each_index { |i| r = rand(length)
irb(main):004:3> self[i],self[r] = self[r],self[i] }
irb(main):005:2> end
irb(main):006:1> end
=> nil
irb(main):007:0> a = [1,2,3,4,5,6,7,8,9,10]
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
irb(main):008:0> a.shuffle
=> [8, 7, 1, 4, 9, 10, 3, 2, 6, 5]
irb(main):009:0> a.shuffle
=> [7, 10, 5, 9, 8, 1, 6, 3, 4, 2]
irb(main):010:0>What did you do differently? Note that if you miss a
bracket or an ‘end’
then irb may think you are in a continuation line; if the
prompt ends with
an asterisk this is a pretty strong clue.irb(main):012:0> [
irb(main):013:1* 1,2,3
irb(main):014:1> ]
=> [1, 2, 3]Regards,
Brian.
Your coding works fine in IRB. The original poster wrote a
= Array[1,2,3,4,5,6,7,8,9,10] which did not work. Get rid
of “Array” and it works.
Joe Gwozdecki
Houston, Texas
On Wed, Jul 09, 2003 at 06:05:28AM +0900, Joe Gwozdecki wrote:
It looks OK to me:
irb(main):001:0> a = Array[1,2,3,4,5]
=> [1, 2, 3, 4, 5]
irb(main):002:0>
(this is 1.6.8)
On Wed, Jul 09, 2003 at 08:46:38AM +0900, Joe Gwozdecki wrote:
Your coding works fine in IRB. The original poster wrote a
= Array[1,2,3,4,5,6,7,8,9,10] which did not work. Get rid
of “Array” and it works.
“Brian Candler” B.Candler@pobox.com wrote in message
news:20030709073944.GA75875@uk.tiscali.com…
Your coding works fine in IRB. The original poster
wrote a
= Array[1,2,3,4,5,6,7,8,9,10] which did not work. Get
rid
of “Array” and it works.It looks OK to me:
irb(main):001:0> a = Array[1,2,3,4,5]
=> [1, 2, 3, 4, 5]
irb(main):002:0>(this is 1.6.8)
I got the error from – a = array[1,2,3,4,5]
IRB will give a consistent error.
You are right. a = Array[1,2,3,4,5] does
work just fine. Also a = [1,2,3,4,5] does too
and is probably cleaner.
Joe Gwozdecki
Houston, Texas
On Wed, Jul 09, 2003 at 08:46:38AM +0900, Joe Gwozdecki wrote:
Certainly. Ruby is case-sensitive. You need to call method of ‘Array’,
not ‘array’
Cheers,
Brian.
On Wed, Jul 09, 2003 at 08:50:59PM +0900, Joe Gwozdecki wrote:
It looks OK to me:
irb(main):001:0> a = Array[1,2,3,4,5]
=> [1, 2, 3, 4, 5]
irb(main):002:0>(this is 1.6.8)
I got the error from – a = array[1,2,3,4,5]
IRB will give a consistent error.
It’s not Array., but Kernel#Array.
On Wed, Jul 09, 2003 at 09:35:22PM +0900, Brian Candler wrote:
On Wed, Jul 09, 2003 at 08:50:59PM +0900, Joe Gwozdecki wrote:
It looks OK to me:
irb(main):001:0> a = Array[1,2,3,4,5]
=> [1, 2, 3, 4, 5]
irb(main):002:0>(this is 1.6.8)
I got the error from – a = array[1,2,3,4,5]
IRB will give a consistent error.Certainly. Ruby is case-sensitive. You need to call method of ‘Array’,
not ‘array’
–
_ _
__ __ | | ___ _ __ ___ __ _ _ __
'_ \ /| __/ __| '__ \ / ` | ’ \
) | (| | |__ \ | | | | | (| | | | |
.__/ _,|_|/| || ||_,|| |_|
Running Debian GNU/Linux Sid (unstable)
batsman dot geo at yahoo dot com
Software is like sex; it’s better when it’s free.
– Linus Torvalds
You sure? This is Kernel#Array:
Array(5) #>> [5]
Array(5,6) #>> ArgumentError: wrong # of arguments(2 for 1)
I believe that foo[bar] is a shortcut for
foo.send(:[], bar)
And therefore Array[1,2,3,4,5] is
Array.send(:[], 1, 2, 3, 4, 5)
#=> [1, 2, 3, 4, 5]
or equivalently
Array.[] (1,2,3,4,5)
#=> [1, 2, 3, 4, 5]
i.e. this is a class (singleton) method of Array
Regards,
Brian.
On Wed, Jul 09, 2003 at 09:45:33PM +0900, Mauricio Fernández wrote:
I got the error from – a = array[1,2,3,4,5]
IRB will give a consistent error.Certainly. Ruby is case-sensitive. You need to call method of ‘Array’,
not ‘array’It’s not Array., but Kernel#Array.
I got the error from – a = array[1,2,3,4,5]
IRB will give a consistent error.Certainly. Ruby is case-sensitive. You need to call method of ‘Array’,
not ‘array’It’s not Array., but Kernel#Array.
You sure? This is Kernel#Array:
Shouldn’t have asserted this so strongly as it turns out… I was wrong 
Anyway, this is yet another case of significant spaces in Ruby:
class << Array
alias_method :old, :;
?> def
puts “Array.”
old(*a)
end
end
=> nil
Array[1,2,3]
Array.
=> [1, 2, 3]
Array [1,2,3]
=> [1, 2, 3]
BTW, irb needs the ‘;’ at the end of the second line:
class << Array
alias_method :old, :
?> def
puts “Array.”
old(*a)
end
SyntaxError: compile error
(irb):6: syntax error
from (irb):6
bug?
On Wed, Jul 09, 2003 at 10:02:40PM +0900, Brian Candler wrote:
On Wed, Jul 09, 2003 at 09:45:33PM +0900, Mauricio Fernández wrote:
–
_ _
__ __ | | ___ _ __ ___ __ _ _ __
'_ \ /| __/ __| '__ \ / ` | ’ \
) | (| | |__ \ | | | | | (| | | | |
.__/ _,|_|/| || ||_,|| |_|
Running Debian GNU/Linux Sid (unstable)
batsman dot geo at yahoo dot com
‘Ooohh… “FreeBSD is faster over loopback, when compared to Linux
over the wire”. Film at 11.’
– Linus Torvalds
Ah, I see: foo[bar] => foo. (bar)
foo [bar] => foo( [bar] )
Yuk. This exists in 1.6.8. I guess it mirrors Matz’s change introduced for
1.8:
foo(a+b).c => ( foo(a+b) ).c
foo (a+b).c => foo( (a+b).c )
As for the semicolon, it seems that irb does not play nicely with unusual
symbols:
$ irb
irb(main):001:0> :ok
=> :ok
irb(main):002:0> :
irb(main):003:0* puts “oops”
oops
=> nil
irb(main):004:0>
Cheers,
Brian.