Ruby is an object-oriented programming language where everything is an object. It supports concepts like single inheritance with mixins, duck typing, metaprogramming and concise yet powerful syntax. The document provides examples of an elegant quicksort implementation, a concise filename incrementer method, and a powerful method to traverse a tree structure and yield output.

1. Ruby

2. Facets
of
Ruby
• Object-­‐Oriented
to
the
core
– Everything
is
an
object
– Tight
encapsula<on
– Single
Inheritance,
but
with
mixin
magic
• Dynamic
– Duck
typing
– Advanced
metaprogramming

3. Elegant
def
quicksort(a)
return
a
if
a.length
<=
1
pivot
=
a.shift
split
=
a.partition
{|i|
i
<
pivot}
(quicksort(split[0])
<<
pivot
<<
(quicksort(split[1]))).flatten
end

4. Concise
def
fname_incr(fname)
!File.exists?(fname)
?
fname
:
/([0-­‐9]+)./.match(fname)
?
fname_incr(fname.sub(/([0-­‐9]+)/)
{
|m|
(m.to_i+1).to_s
})
:
fname_incr(fname.sub(/[^.]*/)
{
|m|
m+'1'
})
end

5. Powerful
def
traverse_tree(addition
=
'',
&proc)
yield
addition
+
"Q:
#{self.value}"
depth
=
$total_height
-­‐
self.height
#
add
1
to
depth
because
the
root
node
has
a
depth
of
0
self.yes.traverse_tree("n"+"t"*(depth+1),
&proc)
self.no.traverse_tree("n"+"t"*(depth+1),
&proc)
end