Rand random. You've got to be kidding

ruby-talk
1

In a message dated 11/28/2006 11:08:19 A.M. US Mountain Standard Tim,
brabuhr@gmail.com writes:

Surely it must be possible to initialize rand with current date and time.
Documents seem to indicate this is done with rand(0) or srand with no

value. I

have tried both methods and I get the same tired old sequence of numbers. I
would write my own random number generator except I don't know how to get a
numeric value out of Time.

Can you post the code that isn't working for you?

I was running the following in SciTE
class Dominoes
attr_writer :deck
def initialize(number)
@deck= Array.new
0.upto(number) {|i| 0.upto(i) {|j| @deck.push([i, j])}}
end

def shuffle!
@deck = @deck.sort{rand}
p @deck
end
end

a=Dominoes.new(6)
a.shuffle!

The p @deck was added so I could see what was being done.

Every time I press F5 I get exactly the same result:
[[6, 6], [4, 4], [0, 0], [5, 0], [1, 1], ...
I get the same results if I wait a few minutes or come back the next day. I
get exactly the same results when I use fxri and freeRIDE. I am running Ruby
version 1.18.4.

Charlie

2

In a message dated 11/28/2006 11:08:19 A.M. US Mountain Standard Tim,
brabuhr@gmail.com writes:

Surely it must be possible to initialize rand with current date and time.
Documents seem to indicate this is done with rand(0) or srand with no value. I
have tried both methods and I get the same tired old sequence of numbers. I
would write my own random number generator except I don't know how to get a
numeric value out of Time.

Can you post the code that isn't working for you?

Please quote your replies correctly.

I was running the following in SciTE
class Dominoes
attr_writer :deck
def initialize(number)
@deck= Array.new
0.upto(number) {|i| 0.upto(i) {|j| @deck.push([i, j])}}
end

def shuffle!
@deck = @deck.sort{rand}

You want @deck = @deck.sort_by { rand }

p @deck
end

a=Dominoes.new(6)
a.shuffle!

The p @deck was added so I could see what was being done.

Every time I press F5 I get exactly the same result:
[[6, 6], [4, 4], [0, 0], [5, 0], [1, 1], ...
I get the same results if I wait a few minutes or come back the next day. I
get exactly the same results when I use fxri and freeRIDE. I am running Ruby
version 1.18.4.

Try:

10.times do puts rand end

then:

srand Time.now.to_i

10.times do puts rand end

···

On Nov 28, 2006, at 1046 , Smgspices@aol.com wrote:

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net
This implementation is HODEL-HASH-9600 compliant

http://trackmap.robotcoop.com

3

Your problem is with
@deck.sort{rand}

------------------------------------------------------------- Array#sort
     array.sort -> an_array array.sort {| a,b | block } -> an_array

···

------------------------------------------------------------------------
     Returns a new array created by sorting _self_. Comparisons for the sort will be done using the +<=>+ operator or using an optional code block. The block implements a comparison between _a_ and _b_, returning -1, 0, or +1. See also +Enumerable#sort_by+.
                                                                                a = [ "d", "a", "e", "c", "b" ] a.sort #=> ["a", "b", "c", "d", "e"] a.sort {|x,y| y <=> x } #=> ["e", "d", "c", "b", "a"]

rand produces always produces values between 0 and 1 so it will always sort the same :slight_smile:

so you need something like this

@deck.sort { if rand < 0.5 then -1; else 1; end }
                                                         
Ken

Smgspices@aol.com wrote:

In a message dated 11/28/2006 11:08:19 A.M. US Mountain Standard Tim, brabuhr@gmail.com writes:

Surely it must be possible to initialize rand with current date and time.
Documents seem to indicate this is done with rand(0) or srand with no
    

value. I
  

have tried both methods and I get the same tired old sequence of numbers. I
would write my own random number generator except I don't know how to get a
numeric value out of Time.
    
Can you post the code that isn't working for you?

I was running the following in SciTE
class Dominoes
attr_writer :deck
def initialize(number)
@deck= Array.new
0.upto(number) {|i| 0.upto(i) {|j| @deck.push([i, j])}}
end

def shuffle!
@deck = @deck.sort{rand}
p @deck
end
a=Dominoes.new(6)
a.shuffle!
The p @deck was added so I could see what was being done.
Every time I press F5 I get exactly the same result:
[[6, 6], [4, 4], [0, 0], [5, 0], [1, 1], ...
I get the same results if I wait a few minutes or come back the next day. I get exactly the same results when I use fxri and freeRIDE. I am running Ruby version 1.18.4.
Charlie