max pleaner - 1 year ago 108
Ruby Question

# coin flipper with N probability of heads

The goal is to flip a weighted coin such that it returns heads N percent of the time.

I'm not totally stumped here. I can do it this way:

probability = 0.75 # chance of getting heads as decimal
(100 - num_heads_cases).times.map { :tails }
)

But I'm posting here to see if there's not some core ruby / rails method I'm overlooking. I'm looking for something similar to the following method signature:

def random_bool(probability_of_returning_true=0.5)

This is similar to the question it's marked as a duplicate of but is not a duplicate; that question asks how to get a random number, while this one asks how to get a random boolean with probability.

It might seem obvious how to go from "random number" to "random boolean" but it's evidently not that way to everyone.

def rb(prob=0.5)
rand < prob
end

10.times.map { rb(0.8) }
#=> [true, true, false, false, true, false, true, true, true, true]

100.times.reduce(0) { |t,_| t + (rb(0.8) ? 1 : 0) }/100.0
#=> 0.87

1000.times.reduce(0) { |t,_| t + (rb(0.8) ? 1 : 0) }/1000.0
#=> 0.798

10000.times.reduce(0) { |t,_| t + (rb(0.8) ? 1 : 0) }/10000.0
#=> 0.8003
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