From: "Ruy Díaz Jara" <diazruy@...>
Date: 2007-04-30T03:04:36+09:00
Subject: [QUIZ] Checking Credit Cards (#122)

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Hi everyone, like most of the other quiz solvers, I am also new to Ruby and
the mailing list. This is my second Ruby program, so I am eagerly awaiting
any comments on improvements, flaws, etc. Without further ado, my code:

------------------------------------------------------

@card_types = [
  ["Mastercard",/^5[1-5]\d{14}$/],
  ["Visa",/^4(\d{12}|\d{15})$/],
  ["Discover",/^6011\d{12}$/],
  ["AMEX",/^3[47]\d{13}$/],
  ["Unknown",/^\d*$/]
 ]

def card_type( card_number )
  card_number.gsub!( /\s/, '')
  @card_types.each do |card_type|
    return card_type[0] if card_type[1] =~ card_number
  end
  raise "Invalid characters in input"
end

def luhn( card_number )
  sum = 0
  card_number.length.downto( 1 ) do |i|
    doubled = ( i%2 + 1 ) * ( card_number[ i-1, 1 ].to_i )
    if doubled >= 10
      doubled = (doubled  % 10 ) + 1
    end
    sum += doubled
  end
  sum % 10 == 0
end

def validate( card_number )
  return card_type( card_number ), luhn( card_number )
end

p validate( ARGV.join.gsub( /\s/, '') )

--------------------------------

Ruy

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