Can I create an array in Ruby with default values?

Question

Perl is pretty nice about default values:

: jmglov@laurana; perl -e \'@foo; printf \"%d\\n\", $foo[123]\'
0
: jmglov@laurana; perl -e \'%foo; printf \"%d\\n\         


        

Answer 1

Given that Ruby returns nil for a non-existing element (as opposed to index-out-of-bounds type error), you could just use an "or":

a = [1,2,3]
puts a[5]  # => nil
puts a[5] || "a default"  # => a default

You could take the monkey patch approach, but you probably would not want to do this in anything larger than a 1-file script:

a = [1,2,3]
def a.[](index)
  self.at(index) || "a default"
end
puts a[5]   # => "a default"