# Question abour rand()

Dear Sirs,

I’m looking for a way to create a random sequence of numbers using the
‘rand’ method. I can think of something like:

## while pipi == TRUE if x > 1950 || x < 2000 return x pipi = FALSE

Since however the book that I’m reading has not introduced while/else/if
etc. I’m thinking that there must be an easier and probably more
sensible way to approach this. As far as I’ve read rand(2000) will give
random numbers from 0-to-2000 no matter what.

NOTE: I don’t want to use another method just to do the job.

thanks in advance & best regards

Panagiotis (atmosx) Atmatzidis

email: [email protected]
URL: http://www.convalesco.org
GnuPG ID: 0xFC4E8BB4
gpg --keyserver x-hkp://pgp.mit.edu --recv-keys 0xFC4E8BB4

Hello,

I’m looking for a way to create a random sequence of numbers using the ‘rand’ method. I can think of something like:

while pipi == TRUE
if x > 1950 || x < 2000

Perhaps you were thinking of “and” rather than “or” because all number
is either greater than 1950 or smaller than 2000.

Since however the book that I’m reading has not introduced while/else/if etc. I’m thinking that there must be an easier and probably more sensible way to approach this. As far as I’ve read rand(2000) will give random numbers from 0-to-2000 no matter what.

Does ‘rand(50) + 1950’ do what you want ?

Cheers,

On 2009-12-29, Panagiotis A. [email protected] wrote:

while pipi == TRUE
if x > 1950 || x < 2000
return x
pipi = FALSE

Hmm. Looks as though you want the range 1951…1999. Well, that’s easy
enough:

rand(49) + 1951

(Note that rand(49) returns anything from 0 to 48, inclusive.)

-s

Panagiotis A. wrote:

Dear Sirs,

I’m looking for a way to create a random sequence of numbers using the
‘rand’ method. I can think of something like:

## while pipi == TRUE if x > 1950 || x < 2000 return x pipi = FALSE

Since however the book that I’m reading has not introduced while/else/if
etc. I’m thinking that there must be an easier and probably more
sensible way to approach this. As far as I’ve read rand(2000) will give
random numbers from 0-to-2000 no matter what

Use Seebs’ suggestion.

NOTE: I don’t want to use another method just to do the job.

Then you are probably being silly. It will make for more readable and
more reusable code if you encapsulate this in a method. Having lots of
short methods is generally a good thing.

thanks in advance & best regards

Panagiotis (atmosx) Atmatzidis

email: [email protected]
URL: http://www.convalesco.org
GnuPG ID: 0xFC4E8BB4
gpg --keyserver x-hkp://pgp.mit.edu --recv-keys 0xFC4E8BB4

## Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

Hi,

Am Dienstag, 29. Dez 2009, 18:51:53 +0900 schrieb Panagiotis A.:

NOTE: I don’t want to use another method just to do the job.

thanks in advance & best regards

The “rand” method has been mentioned. Here are just some

You don’t need a loop for calculating a random value. (There is a
random algorithm below.) But when use a loop, then you either say
“return” or leave it by a condition but not both.

cond = true
while cond do

if some_condition then
cond = false
end

end

or

loop do

break if some_condition

end

Note that “break” can even return values:

result = loop do
break “hi”
end
result == “hi”

And here is an example of a very simple random implementation:

class R
def initialize
@r = 0
end
def nextval
@r = ((@r * 0xabcd) + 0x73737) % 0x1_0000_0000
@r >> 16
end
end
r = R.new
new_random_value = r.iterate
random_value_below_fifty = r.iterate % 50

Bertram

On 29.12.2009 18:00, Marnen Laibow-Koser wrote:

NOTE: I don’t want to use another method just to do the job.

Then you are probably being silly. It will make for more readable and
more reusable code if you encapsulate this in a method. Having lots of
short methods is generally a good thing.

“Walk before you run.”

Panagiotis A. wrote:

I’m looking for a way to create a random sequence of numbers using the
‘rand’ method.

Others have answered the ‘random number between 1950 and 2000’ bit.

In terms of creating a “sequence” of these values, here are a couple of
options to consider.

(1) Build an array.

a = []
10.times { a << rand(50) }

This array (a) is an object which can be returned, passed to other
functions etc. The above code hard-codes the number of values to build
(10), but you could choose this dynamically at run-time instead.

(2) Yield the values.

For code which wants to “return” multiple values, you can instead
“yield” the values to a block which the caller provides. You can yield
multiple times, thus calling the block multiple times. In other
programming languages you might call this a “callback function”

def generate_random(n=10)
n.times do
yield rand(50)
end
end

generate_random do |r|
puts “I got #{r}!”
end

Note that you can legitimately yield an infinite number of times,
because the block can abort the sequence when it wants. So in the
following example, the user of the function decides when they don’t want
any more random numbers:

def generate_infinite
loop do
yield rand(50)
end
end

count = 0
generate_infinite do |r|
puts “I got #{r}!”
count += 1
break unless count < 10
end

A more advanced way to do this is with an ‘Enumerator’ object, but I’d