Wednesday, February 29, 2012
On Wed, Feb 29, 2012 at 3:05 AM, Robert Walker <lists@ruby-forum.com> wrote:
Another caveat is that the Array contains "Float" objects, while the
original question was "500 unique decimals". Two issues here:
1) if "decimals" are asked in the problem statement, why then do
we serve Floats in the result?
2) The problem is that for uniqueness, we need the '==' operator and
on Floats that represent fractional numbers in the decimal system,
equality is not a stable function (as was discussed many times before ...).
So, in all proposed solutions, I would exchange this line:
> value = Integer((rand * 1) * 1000) / Float(1000)
with this one:
value = rand(1000) / BigDecimal.new(1000)
HTH,
Peter
-- Robert Walker wrote in post #1049376:
> #!/usr/bin/env rubyOne caveat with this technique: Make sure you build in some "circuit
> require 'set'
>
> def random_numbers(n = 500)
> my_set = Set.new
> while my_set.size < 500
> value = Integer((rand * 1) * 1000) / Float(1000)
> my_set << value
> end
> my_set.to_a
> end
>
> puts random_numbers.size
breaker" protection code. The more numbers you ask this to generate the
more rounds it will take to produce the result. Generating 500 unique
numbers is averaging about 700 rounds. The closer to 1000 you get the
more rounds it will take. Over 1000 and it will never finish.
Another caveat is that the Array contains "Float" objects, while the
original question was "500 unique decimals". Two issues here:
1) if "decimals" are asked in the problem statement, why then do
we serve Floats in the result?
2) The problem is that for uniqueness, we need the '==' operator and
on Floats that represent fractional numbers in the decimal system,
equality is not a stable function (as was discussed many times before ...).
So, in all proposed solutions, I would exchange this line:
> value = Integer((rand * 1) * 1000) / Float(1000)
with this one:
value = rand(1000) / BigDecimal.new(1000)
HTH,
Peter
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