# Linked list example
class MyElem
# object initializer called from Class#new
def initialize(item)
# @variables are instance variable, no declaration needed
@data = item
@succ = nil
end
def data
@data
end
def succ
@succ
end
# the method invoked by ``obj.data = val''
def succ=(new)
@succ = new
end
end
class MyList
def add_to_list(obj)
elt = MyElem.new(obj)
if @head
@tail.succ = elt
else
@head = elt
end
@tail = elt
end
def each
elt = @head
while elt
yield elt
elt = elt.succ
end
end
# the method to convert object into string.
# redefining this will affect print.
def to_s
str = "<MyList:\n";
for elt in self
# short form of ``str = str + elt.data.to_s + "\n"''
str += elt.data.to_s + "\n"
end
str += ">"
str
end
end
class Point
def initialize(x, y)
@x = x; @y = y
self
end
def to_s
sprintf("%d@%d", @x, @y)
end
end
# global variable name starts with `$'.
$list1 = MyList.new
$list1.add_to_list(10)
$list1.add_to_list(20)
$list1.add_to_list(Point.new(2, 3))
$list1.add_to_list(Point.new(4, 5))
$list2 = MyList.new
$list2.add_to_list(20)
$list2.add_to_list(Point.new(4, 5))
$list2.add_to_list($list1)
# parenthesises around method arguments can be ommitted unless ambiguous.
print "list1:\n", $list1, "\n"
print "list2:\n", $list2, "\n"
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