From: Francisco Laguna <fla@...>
Date: 2007-06-14T22:06:50+09:00
Subject: "case when" executes a symbol as method

Hi List! 
 
I just stumbled upon some interesting behaviour of case when and wanted 
to ask a few things about it. It looks like the "case when" construct 
executes a method when one leaves a out a newline (or semi-colon, I 
guess) after the when differentiation. Consider these to programs: 
 
=== program 1 ===  
 
def hello 
  "Hello World!" 
end 
 
def good_day 
  "Good Day, World!" 
end 
 
greeting = "Hello" 
 
puts case greeting 
when "Hello"  
  :hello 
when "Good Day"  
  :good_day 
end 
 
=== program 2 === 
 
def hello 
  "Hello World!" 
end 
 
def good_day 
  "Good Day, World!" 
end 
 
greeting = "Hello" 
 
puts case greeting 
when "Hello" :hello 
when "Good Day" :good_day 
end 
 
============== 
 
The first just prints out the symbols turned to strings ("hello" or 
"good_day", respectively), but the second one acrually executes the 
hello and good_day methods and the case block has the return value of 
the methods as its own value. Pretty cool, if you ask me. How come? Is 
that something I can rely on, or something that might disappear, because
it's just some side-effect? 
 
Thanks for the insight 
 Cisco