From: Farhad Farzaneh <ff@...>
Date: 2010-02-19T06:44:21+09:00
Subject: Re: Ruby conditionals subtlety?

Ryan Davis wrote:
> On Feb 18, 2010, at 11:49 , Farhad Farzaneh wrote:
> 
>> Hi,
>> 
>> Anyone know why thse two forms of "unless" behave differently?
>> 
>>> irb
>> irb(main):001:0> foo = true unless defined?(foo)
>> => nil
>> irb(main):002:0> unless defined?(fooo) ; fooo = true ; end
>> => true
> 
> oddity in the way the code is parsed:
> 
> % echo "foo = true unless defined?(foo)" | parse_tree_show
> s(:if, s(:defined, s(:lvar, :foo)), nil, s(:lasgn, :foo, s(:true)))
> 
> % echo "unless defined?(fooo) ; fooo = true ; end" | parse_tree_show
> s(:if, s(:defined, s(:call, nil, :fooo, s(:arglist))), nil, s(:lasgn, 
> :fooo, s(:true)))

Cool, any chance you could give a short description for those of us that 
have never really thought about the parser or used parse_tree_show?

thx

-- 
Posted via http://www.ruby-forum.com/.