Method: Constants::Constant.parse

Defined in:
lib/constants/constant.rb

.parse(str) ⇒ Object

Parses the common notation ‘<value>(<uncertainty>)’ into a value and an uncertainty. When no uncertainty is specified, the uncertainty is nil.

Whitespace is allowed.

Base.parse("1.0(2)").vu                    # => [1.0, 0.2]
Base.parse("1.007 825 032 1(4)").vu        # => [1.0078250321, 1/2500000000]
Base.parse("6.626 068 96").vu              # => [6.62606896, nil]



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# File 'lib/constants/constant.rb', line 39

def parse(str)
  str = str.to_s.gsub(/\s/, '')
  raise "cannot parse: #{str}" unless str =~ /^(-?\d+)(\.\d+)?(\(\d+\))?(e-?\d+)?(.*)$/

  value = "#{$1}#{$2}#{$4}".to_f
  unit = $5
  uncertainty = case
  when $3 == nil then nil
  else
    factor = $2 == nil ? 0 : 1 - $2.length
    factor += $4[1..-1].to_i unless $4 == nil
    $3[1..-2].to_i * 10 ** factor
  end

  block_given? ? yield(value, unit, uncertainty) : new(value, unit, uncertainty)
end