Generating a Specified Length String of Random Numbers

[bivouac]

This is going to sound like a homework question, but I swear I'm not in school. So bear with me.

Here's some pseudo-code that I wrote up.

# I want to be able to create a random numeric string that is the length
# specified by the user. I should take an integer as input and this should
# correspond to the length of the string. I should generate random
# numbers for each positional length until the string is equal to the length
# specified by the user.

Here's where I'm stuck:

  # makes a new string with zero length
    n = String.new
    
    # function to return random numbers
    # don't want any zeroes and I think
    # i need to return the val as a string
    # and not an integer hence the 'to_s'
    def generateChar
      i = rand(8) + 1
      return i.to_s
    end
    
    # could be a 'while' - trying until
    # call the generateChar function
    # until the length of the new string
    # is equal to 10. length here is hardcoded
    # but eventually would be a var
    until n.length = 10
      n + generateChar()
      return n
    end
    
    # yep, generateChar() function works
    # puts generateChar()
    
    puts n

Not sure where to go here. In PHP you can concatenate strings using the '.=' operator.

To concat in Ruby you use the '+' operator, but I think there's something else wrong in what I'm trying to do.

[sweatje]

perhaps something like

>> n=7
=> 7
>> (rand(8)+1).to_s+((1..n).collect {rand(9).to_s}).join
=> "22538535"
>> n=12
=> 12
>> (rand(8)+1).to_s+((1..n).collect {rand(9).to_s}).join
=> "7285886160030"

[bivouac]

Jason -

Love your articles, by the way. And the PHP slides - the SimpleTest slides immeasurably helpful.

Can you explain that just a little? I think I see what you're doing, but I don't really get it. There's a range in there and a new method 'collect' that I've never used. Didn't dawn on me to use 'join.'

[sweatje]

Thanks.

I just made the first character, then I used the range to specify how many iterate. collect took a block which returned another digit as a string. join took that resulting array and assembled it back into a string.

Also, take this with a grain of salt, I am probably just as much of a newby at Ruby as you are.

[stereofrog]

Tim Toady on the ruby track

len = 10

s = (1..len).inject("") { |s, x| 
	s << rand(9).to_s }

# dumb and dumber but perhaps more readable
s = ''
len.times { s << rand(9).to_s }

Also, take this with a grain of salt, I am probably just as much of a newby at Ruby as you are.

Same here

[sweatje]

actually, just realized there is a bug there the range should be (1...n) to get n chars in the resulting string

[Fenrir2]

until n.length = 10

Should be == (in PHP too).

.= is += in ruby. The types need to match though.