Folks,
I'm trying to generate a random number between (0..10) less, say, 5.
new_index = rand(0..(old_index - 1)) || new_index = rand((old_index + 1)..10)
Can anyone shed any light?
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1Possible duplicate of [How to get a random number in Ruby?](http://stackoverflow.com/questions/198460/how-to-get-a-random-number-in-ruby) – Alexander Derck Jan 17 '16 at 19:46
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hmm if you remove one element, that's not a range anymore. Any reason why you can't use an Array? – cozyconemotel Jan 17 '16 at 19:47
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1I have absolutely no idea what your question is about. – sawa Jan 17 '16 at 20:03
1 Answers
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new_sample_space = (0..10).to_a - [5] #=> [0, 1, 2, 3, 4, 6, 7, 8, 9, 10]
new_index = new_sample_space.sample #=> random integer from 0-10, except 5
Of course, doing this with a large range is probably not a good idea because of memory concerns. In such "huge" cases, you could possibly just get another random number after you get 5.
loop do
new_index = rand(1..10)
break if new_index != 5
end
cozyconemotel
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Your second code has a high probability that it will terminate correctly, but it has a small chance that it will take a long time to terminate or run into an infinite loop. The probability that it will terminate in `n` iterations is `1 - (1/10)^n`. – sawa Jan 17 '16 at 20:31
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You're right, and that's why I limited its use to "huge" cases.. `(0..100000000).to_a` is expensive but `rand(1..100000000)` is fast and the probability that it will terminate in `n` iterations is `1 - (1/100000000)^n`.. well yeah it's probably not a good idea in production anyways – cozyconemotel Jan 17 '16 at 22:15