TryCatchWithRubyBlocks

Last edit January 30, 2009

RenameMe to ContinuationsInRuby ?

People on BlocksInPython want to see TryCatch implemented in RubyLanguage. I won't dive in a SchemeLanguage-like continuation-based ErrorHandling, just note that this (somewhat) already exists:

 def routine(n)
  puts n
  throw :done if n <= 0
  routine(n-1)
 end

 catch(:done) do
  routine(3)
 end

RubyLanguage's 'throw' and 'catch' is GoTo. GoTo has its uses, but for conventional ErrorHandling use 'raise' and 'rescue':

 def factorial(n)
   raise ArgumentError, "factorial arg must be >= 0: #{n}" unless n >= 0
   return 1 if n.zero?
   (1..n).inject(1) { |product, i| product * i }
 end

 while true
   print 'Enter a number (-1 to quit): '
   n = gets.to_i
   exit if n == -1
   begin
     puts "#{n}! = #{factorial(n)}"
   rescue ArgumentError => e
     puts e
   end
 end

CategoryRuby