'400'.to_i

'3.14'.to_f

'1.602e-19'.to_f

'405'.oct

'405'.to_i(8)

'405'.hex

'405'.to_i(16)

'fed'.hex

'fed'.to_i(16)

"13: a baker's dozen".to_i

'1001 Nights'.to_i

'The 1000 Nights and a Night'.to_i

'60.50  Misc. Agricultural Equipment'.to_f

'$60.50'.to_f

'Feed the monster!'.hex

'I fed the monster at Canoga Park Waterslides'.hex

'0xA2Z'.hex

'-10'.oct

'-109'.oct

'3.14'.to_i

Integer('1001')

Integer('1001 nights')

ArgumentError: invalid value for Integer: "1001 nights"
...

ArgumentError: invalid value for Integer: "1001 nights"
	from (irb):22:in `Integer'
	from (irb):22

Float('99.44')

Float('99.44% pure')

ArgumentError: invalid value for Float(): "99.44% pure"
...

ArgumentError: invalid value for Float(): "99.44% pure"
	from (irb):24:in `Float'
	from (irb):24

class NumberParser
  @@number_regexps = { 
    :to_i => /([+-]?[0-9]+)/,
    :to_f => /([+-]?([0-9]*\.)?[0-9]+(e[+-]?[0-9]+)?)/i,
    :oct => /([+-]?[0-7]+)/,
    :hex => /\b([+-]?(0x)?[0-9a-f]+)\b/i
    #The \b characters prevent every letter A-F in a word from being
    #considered a hexadecimal number.
  }
  def NumberParser.re(parsing_method=:to_i)
    re = @@number_regexps[parsing_method] 
    raise ArgumentError, "No regexp for #{parsing_method.inspect}!" unless re
    return re
  end
  def extract(s, parsing_method=:to_i)
    numbers = []
    s.scan(NumberParser.re(parsing_method)) do |match| 
      numbers << match[0].send(parsing_method) 
    end
    numbers
  end
end
p = NumberParser.new
pw = "Today's numbers are 104 and 391."
NumberParser.re(:to_i).match(pw).captures

p.extract(pw, :to_i)

p.extract('The 1000 nights and a night')

p.extract('$60.50', :to_f)

p.extract('I fed the monster at Canoga Park Waterslides', :hex)

p.extract('In octal, fifteen is 017.', :oct)

p.extract('From 0 to 10e60 in -2.4 seconds', :to_f)

p.extract('From 0 to 10e60 in -2.4 seconds')

require 'scanf'
s = '0x10 4.44 10'.scanf('%x %f %d')