Add Specify How Random Array Sample Is as a Ruby TIL

ruby/specify-how-random-array-sample-is.md

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+# Specify How Random Array#sample Is
+
+A typical use of the
+[`sample`](https://ruby-doc.org/core-2.4.0/Array.html#method-i-sample) method
+on [`Array`](https://ruby-doc.org/core-2.4.0/Array.html) will look something
+like this:
+
+```ruby
+> chars = [('a'..'z'), ('A'..'Z'), ('0'..'9')].map(&:to_a).flatten
+
+> chars.sample(6)
+=> ["o", "Z", "X", "i", "8", "Y"]
+```
+
+By default, this is using `Random` (a pseudo-random number generator) to
+produce a _random_ sampling of elements from your array.
+
+The longer form of this looks like:
+
+```ruby
+> chars.sample(6, random: Random)
+=> ["F", "c", "g", "I", "w", "E"]
+```
+
+Or to get reproducible results, you can specify the `Random` seed:
+
+```ruby
+> chars.sample(6, random: Random.new(123))
+=> ["T", "c", "D", "K", "P", "s"]
+```
+
+If instead you want a cryptographically random sampling of elements from your
+array, you can specify a different random number generator. Such as
+[`SecureRandom`](https://ruby-doc.org/stdlib-2.5.1/libdoc/securerandom/rdoc/SecureRandom.html).
+
+```ruby
+> require 'securerandom'
+=> true
+
+> chars.sample(6, random: SecureRandom)
+=> ["3", "C", "o", "i", "K", "4"]
+```
+
+The
+[`Array#shuffle`](https://ruby-doc.org/core-2.4.0/Array.html#method-i-shuffle)
+method is another example of a method that can take a `random` option.