#!/usr/bin/env ruby

# =========================================================================
#	NeverEnding.rb
#	J. Menu - http://cui.unige.ch/DI/cours/CompInterpretes
#
#	$Id$
# =========================================================================


#	The following functions are in fact methods in Ruby


#	A function that cannot be evaluated, whatever it's argument

def NeverEnding (n)
	1 + NeverEnding(n + 1)
end


#	A function that illustrates the virtues of closures

def funct (m, n)
	if m.call < 100
			m.call + 12
	else
			n.call
	end
end


puts "\n==> An interesting programming example...\n\n"


# Call by name will compute "funct" fine!

puts "--> Calling 'funct' with closures, thus mimicking call by name"

printf(
  "%d\n\n",
  funct(
    lambda { || 3 + 5 },
    lambda { || NeverEnding(7) }
    )
  )


# Call by value will just defeat it!

puts "--> Calling 'funct' without closures, i.e. with mere call by value"

printf("%d\n", funct(3 + 5, NeverEnding(7)))