Array.shuffle/Array.shuffle!

[Jeff Moore]

This works but I can't escape the nagging sense that there's a more
concise approach (for one thing, it looks like there are way too
transient objects to me).

Anyone have a better idea?


class Array

def shuffle
t_self = self.dup
t_size = self.size
result=[]
t_size.times { result << t_self.slice!(rand(t_self.size)) }
result
end

def shuffle!
t_self = self.dup
t_size = self.size
self.clear
t_size.times { self << t_self.slice!(rand(t_self.size)) }
self
end

end


Regards...

 

[Tim Hunter]

This works but I can't escape the nagging sense that there's a more
concise approach (for one thing, it looks like there are way too
transient objects to me).

Anyone have a better idea?

ary2 = ary.sort_by { rand }

 

[Jeff Moore]

ary2 = ary.sort_by { rand }

"Gone in 60 seconds"...

Thanks

 

[Stefan Rusterholz]

This works but I can't escape the nagging sense that there's a more
concise approach (for one thing, it looks like there are way too
transient objects to me).

Anyone have a better idea?


class Array

def shuffle
t_self = self.dup
t_size = self.size
result=[]
t_size.times { result << t_self.slice!(rand(t_self.size)) }
result
end

def shuffle!
t_self = self.dup
t_size = self.size
self.clear
t_size.times { self << t_self.slice!(rand(t_self.size)) }
self
end

end


Regards...

If you need a less predictable one than the sort_by { rand } then I
suggest this:

class Array
# Shuffle the array
def shuffle!
n = length
for i in 0...n
r = Kernel.rand(n-i)+i
self[r], self = self, self[r]
end
self
end

# Return a shuffled copy of the array
def shuffle
dup.shuffle!
end
end

This shuffle is known as fisher-yates/knuth shuffle and is afaik by
current means considered impossible to predict. Also its complexity is
O(n) compared to the O(nlogn) of sort_by (which for many cases probably
still is faster in ruby since it runs mainly in C, I didn't bench it,
though).

As of 1.8.7 you have those methods already natively provided by ruby.

Regards
Stefan (apeiros)

 

[Jeff Moore]

As of 1.8.7 you have those methods already natively provided by ruby.

Regards
Stefan (apeiros)

Ah! If only the Ubuntu/Debian promotion cycle for Ruby out paced
continental drift...

Thanks again...

I appreciate it.

 

[Joel VanderWerf]

Ah! If only the Ubuntu/Debian promotion cycle for Ruby out paced
continental drift...

I heard the 9.04 release will be called Galloping Gondwanaland.

 

[Alexei Broner]

No, 'I' is next in line. "Irresponsible Irmin"

I heard the 9.04 release will be called Galloping Gondwanaland.