class Array

# File lib/uk_account_validator/backports/array_bsearch_index.rb, line 4
def bsearch_index
  return to_enum(__method__) unless block_given?
  from = 0
  to   = size - 1
  satisfied = nil
  while from <= to do
    midpoint = (from + to).div(2)
    result = yield(self[midpoint])
    case result
    when Numeric
      return midpoint if result == 0
      result = result < 0
    when true
      satisfied = midpoint
    when nil, false
      # nothing to do
    else
      raise TypeError, "wrong argument type #{result.class} (must be numeric, true, false or nil)"
    end

    if result
      to = midpoint - 1
    else
      from = midpoint + 1
    end
  end
  satisfied
end