How to generate a random number between a and b in Ruby?
RubyRandomRangeRuby Problem Overview
To generate a random number between 3 and 10, for example, I use: rand(8) + 3
Is there a nicer way to do this (something like rand(3, 10)) ?
Ruby Solutions
Solution 1 - Ruby
UPDATE: Ruby 1.9.3 Kernel#rand also accepts ranges
rand(a..b)
http://www.rubyinside.com/ruby-1-9-3-introduction-and-changes-5428.html
Converting to array may be too expensive, and it's unnecessary.
(a..b).to_a.sample
Or
[*a..b].sample
Standard in Ruby 1.8.7+.
Note: was named #choice in 1.8.7 and renamed in later versions.
But anyway, generating array need resources, and solution you already wrote is the best, you can do.
Solution 2 - Ruby
Random.new.rand(a..b)
Where a is your lowest value and b is your highest value.
Solution 3 - Ruby
rand(3..10)
> When max is a Range, rand returns a random number where range.member?(number) == true.
Solution 4 - Ruby
Just note the difference between the range operators:
3..10 # includes 10
3...10 # doesn't include 10
Solution 5 - Ruby
def random_int(min, max)
rand(max - min) + min
end
Solution 6 - Ruby
See this answer: there is in Ruby 1.9.2, but not in earlier versions. Personally I think rand(8) + 3 is fine, but if you're interested check out the Random class described in the link.
Solution 7 - Ruby
For 10 and 10**24
rand(10**24-10)+10
Solution 8 - Ruby
And here is a quick benchmark for both #sample and #rand:
irb(main):014:0* Benchmark.bm do |x|
irb(main):015:1* x.report('sample') { 1_000_000.times { (1..100).to_a.sample } }
irb(main):016:1> x.report('rand') { 1_000_000.times { rand(1..100) } }
irb(main):017:1> end
user system total real
sample 3.870000 0.020000 3.890000 ( 3.888147)
rand 0.150000 0.000000 0.150000 ( 0.153557)
So, doing rand(a..b) is the right thing