Methods in ruby code

addis_a · October 10, 2013, 7:04pm

Hi,

I want to use the shuffle method for array, but I want to modify it a
little bit.
Is there any website or source where I can see the shuffle method in
ruby code, because often in Tutorials they show some of these methods in
Ruby Code and how they look in the libary.
I am looking forward to hear from you.

Yours sincerely
Greeneco

greeneco · October 10, 2013, 7:14pm

On Thu, Oct 10, 2013 at 7:04 PM, Green E. [email protected] wrote:

I want to use the shuffle method for array, but I want to modify it a
little bit.

I would not change the library method but rather implement another
shuffle.

What modifications do you want to do?

Is there any website or source where I can see the shuffle method in
ruby code, because often in Tutorials they show some of these methods in
Ruby Code and how they look in the libary.
I am looking forward to hear from you.

You can try to read the C source - it’s usually not too hard to
understand.

Kind regards

robert

greeneco · October 10, 2013, 7:22pm

Hi,
thanks for your quick answer.
I want to use shuffle but I want it to take parameter and act the same
if I give it the same parameter.
e.g
[1,2,3].shuffle!(5) #=> [2,1,3]
and when I do this again
[1,2,3].shuffle!(5) #=> [2,1,3]
and when I use a different number
[1,2,3].shuffle!(4) #=> [1,2,3]
there should be a different result

I want to do something like that.

King regards
Greeneco

greeneco · October 10, 2013, 8:02pm

Yes you are right it would not be shuffle anymore.
And thank you for your two solutions, but the second one has less
sideeffects but I cannot just use this if I do not close the programm
without saving, because then it would be lost every time I restart. The
first has side effects but I guess it is that what I am looking for.

But what do you think of:
ary = [“1”, “2”, “3”, “4”, “5”, “6”, “7”, “8”, “9”]
number = 9
ary_zahlen.shuffle!(random: Random.new(number))

Yours sincerely
Greeneco

greeneco · October 10, 2013, 7:46pm

On Thu, Oct 10, 2013 at 7:22 PM, Green E. [email protected] wrote:

there should be a different result
But then it’s not shuffle any more, is it? You basically associate a
particular order with a number as key. I can think of two approaches:

manipulate the random generator via the seed:

irb(main):001:0> a = (1…5).to_a
=> [1, 2, 3, 4, 5]
irb(main):002:0> srand 0
=> 38759114252116045413516501677716616995
irb(main):003:0> a.shuffle
=> [1, 4, 2, 5, 3]
irb(main):004:0> srand 0
=> 0
irb(main):005:0> a.shuffle
=> [1, 4, 2, 5, 3]
irb(main):006:0> srand 4
=> 0
irb(main):007:0> a.shuffle
=> [1, 2, 4, 3, 5]
irb(main):008:0> srand 4
=> 4
irb(main):009:0> a.shuffle
=> [1, 2, 4, 3, 5]

use a Hash to store the fixed relation:

irb(main):011:0> a = (1…5).to_a
=> [1, 2, 3, 4, 5]
irb(main):012:0> cache = Hash.new {|h,k| h[k] = a.shuffle}
=> {}
irb(main):013:0> cache[0]
=> [5, 3, 1, 4, 2]
irb(main):014:0> cache[0]
=> [5, 3, 1, 4, 2]
irb(main):015:0> cache[5]
=> [5, 2, 3, 1, 4]
irb(main):016:0> cache[5]
=> [5, 2, 3, 1, 4]
irb(main):017:0> cache[5]
=> [5, 2, 3, 1, 4]
irb(main):018:0> cache[2]
=> [5, 4, 2, 1, 3]
irb(main):019:0> cache[2]
=> [5, 4, 2, 1, 3]
irb(main):020:0> cache
=> {0=>[5, 3, 1, 4, 2], 5=>[5, 2, 3, 1, 4], 2=>[5, 4, 2, 1, 3]}

I’d prefer approach 2 because that does not have side effects on other
parts of the program which want to generate random numbers.

Kind regards

robert

greeneco · October 10, 2013, 9:09pm

Am 10.10.2013 19:04, schrieb Green E.:

I want to use the shuffle method for array, but I want to modify it a
little bit.
Is there any website or source where I can see the shuffle method in
ruby code, because often in Tutorials they show some of these methods in
Ruby Code and how they look in the libary.
I am looking forward to hear from you.

There is a GitHub mirror of the source code:

GitHub - ruby/ruby: The Ruby Programming Language

Array#shuffle is not implemented in Ruby but in C,
you can find it here:

https://github.com/ruby/ruby/blob/trunk/array.c (line 4381)

Regards,
Marcus

greeneco · October 10, 2013, 9:17pm

Am 10.10.2013 19:45, schrieb Robert K.:

[1,2,3].shuffle!(4) #=> [1,2,3]
=> 38759114252116045413516501677716616995
irb(main):008:0> srand 4
irb(main):013:0> cache[0]
=> [5, 4, 2, 1, 3]
robert
Regarding side effects:

Looking at the source code, I just noticed you can pass a random
generator to shuffle. From the ri documentation:

shuffle → new_ary
shuffle(random: rng) → new_ary

Returns a new array with elements of self shuffled.

a = [ 1, 2, 3 ] #=> [1, 2, 3]
a.shuffle #=> [2, 3, 1]

The optional rng argument will be used as the random number generator.

a.shuffle(random: Random.new(1)) #=> [1, 3, 2]

It seems to be there since 1.9.3!
This would solve the side effect problem.

Regards,
Marcus

greeneco · October 11, 2013, 1:14pm

On Thu, Oct 10, 2013 at 9:16 PM, [email protected] wrote:

Am 10.10.2013 19:45, schrieb Robert K.:

a = [ 1, 2, 3 ] #=> [1, 2, 3]
a.shuffle #=> [2, 3, 1]

The optional rng argument will be used as the random number generator.

a.shuffle(random: Random.new(1)) #=> [1, 3, 2]

It seems to be there since 1.9.3!
This would solve the side effect problem.

I had tried that (actually it was my first attempt) but to no avail:

irb(main):001:0> (1…10).to_a.shuffle nil
ArgumentError: wrong number of arguments (1 for 0)
from (irb):1:in shuffle' from (irb):1 from /usr/bin/irb:12:in ’
irb(main):002:0> (1…10).to_a.shuffle Random.new
ArgumentError: wrong number of arguments (1 for 0)
from (irb):2:in shuffle' from (irb):2 from /usr/bin/irb:12:in ’
irb(main):003:0> RUBY_VERSION
=> “1.9.3”

Kind regards

robert

greeneco · October 11, 2013, 2:24pm

Excerpts from Robert K.'s message of 2013-10-11 13:13:42 +0200:

This would solve the side effect problem.
from (irb):2:in shuffle' from (irb):2 from /usr/bin/irb:12:in’
irb(main):003:0> RUBY_VERSION
=> “1.9.3”

The random number generator must be passed as a (pseudo) keyword
argument, that is as a hash, either using the new ruby 1.9 syntax, as
shown by the ri documentation:

a.shuffle random: Random.new

or using the standard hash syntax:

a.shuffle :random => Random.new

Stefano

greeneco · October 11, 2013, 2:37pm

On Fri, Oct 11, 2013 at 2:29 PM, Stefano C.
[email protected] wrote:

Excerpts from Robert K.'s message of 2013-10-11 13:13:42 +0200:

On Thu, Oct 10, 2013 at 9:16 PM, [email protected] wrote:

irb(main):002:0> (1…10).to_a.shuffle Random.new
shown by the ri documentation:
Ah! Thanks for the education! I had myself mislead by the
ArgumentError (above). I should have checked #arity

irb(main):001:0> Array.instance_method(:shuffle).arity
=> -1

… or the docs.

Kind regards

robert

greeneco · October 11, 2013, 6:02pm

Hi,

thank you for your big help, you really helped me out.

King regards
Green E.