Rounding values

rounding.rb

#
# Rounds a number
#
# If nearest == pivot, the rounding will always go up.
#
# Default behaviour:
#   round(0) # 10
#   round(1) # 10
#   round(9) # 10
#   round(10) # 20
#   round(19) # 20
#   round(20) # 30
#   round(99) # 100
#   round(100) # 200
#   round(101) # 200
#   round(999) # 1000
#   round(1000) # 2000
#
def round(num, nearest = nil, pivot = nil)
  negative = num < 0                         # record if the number is negative
  num = -num if negative                     # make the number positive
  precision = Math.log10(num).to_i rescue 1  # are we dealing with 10's, 100's, 1000's...
  precision = 1 if precision == 0            # the lowest value we want to round to is 10
  nearest ||= 10**precision                  # the rounding value
  pivot ||= nearest                          # the value that will cause us to round up/down
                                             # NOTE: if pivot == nearest, the rounding will always go up
  result = (num + pivot) / nearest * nearest # perform the rounding
  negative ? -result : result                # make number negative, if required
end