RCR 270: Add clamp(), modulo(), rand() methods to Range

The Range object is <i>under-interpreted</i> as a range. As a Range object is not merely a duple of integers, there is room for more methods which take advantage of its meaning.

The Range class does not include all methods which are common operations on ranges.

• Add rng.clamp(n), which will return the value of n if n is within the range, or otherwise the minimum or maximum points in the range.
• Add rng.modulo(n), which will perform a modulus operation to assure that the return value is a member of rng.
• Similar to a comment in https://rcrchive.net/rcr/RCR/RCR62'>RCR 62, add rng.rand(), which will supply a random number from within the range.

1. in addition to what is already there

class Range

  # returns a value within the range
  # will return lowest or highest
  # value if n is out of range in the
  # lower or upper directions
  # (respectively)
  def clamp(n)
    return first if n<first
    return last-1 if n>last-1 && exclude_end?
    return last if n>last
    n
  end
  # maps n to a value in the range.
  # this comes up in many algorithms.
  def modulo(n)
    n.modulo(length) + first
  end
  # choose a random member of this range
  def rand
    modulo Kernel::rand(length)
  end

end