From: "Peña, Botp" <botp@...>
Date: 2006-08-19T12:41:47+09:00
Subject: Re: Syntax checker wtf?

From: Hal Fulton [mailto:hal9000@hypermetrics.com] 
# Bill Kelly wrote:
# > I wonder...
# > 
# > 0001: class Foo
# > 0002:
# > 0003:   def initialize
# > 0004:     # whatever
# > 0005:   end
# > 0006:
# > [...]
# > 0347:   def bar
# > 0348:     if @gargle
# > 0349:       puts "glug!"
# > 0350:     #end  (missing end for if)
# > 0360:   end
# > [...]
# > 0415:
# > 0416: end    # of class Foo
# > 
# > Now, the error message we'd like is that the 'end' is 
# missing for the 'if'
# > expression starting on line 348.
# > 
# > But the parser did find an 'end' that paired up with the 
# 'if', at line 360.
# > And it found an 'end' for the 'def' at line 416.  
# Ultimately, it reaches 
# > the
# > end of the file, and is missing an 'end' for 'class Foo'.
# > 
# > So, would "unexpected EOF, missing kEND from line 1" really be all
# > that helpful?
# > 
# > It seems like a missing 'end' would probably tend to be reported for
# > whatever line the outermost class or module being compiled started
# > on... (?)
# 
# This is sort of an interesting idea, discussed before. I wonder what
# Matz thinks about it. It's not like "enforcing" indentation, it's just
# using it to "guess" about a syntax error.
# 
# Of course, the way it works now, it DOES find an 'end' for the 'if'...
# it's on line 360. :)  What it doesn't find is an end for the class...
# 
# So unless it was whitespace-sensitive, it would tell you that it
# reached the end of file while parsing the expression that started
# on line 1.  :)

is it possible for ruby to return list of end pairs pretty printed (think folding)? 

Error: unexpected EOF, missing kEND from line 1. 
Listing end pairs encountered:

0001: class Foo
0003:   def initialize
0005:   end
0347:   def bar
0348:     if @gargle
0360:     end
0416:   end    # of class Foo
      <--- missing end here

an intelligent editor may then possibly associate the end pairs with the actual code, like so (pls forgive the crude ascii art),


 0001: class Foo  -------------------------  0001: class Foo
 0003:   def initialize .................    0002:
 0005:   end  ........................   '.. 0003:   def initialize
 0347:   def bar -----------------..  |      0004:     # whatever
 0348:     if @gargle ..........   |  '..... 0005:   end
 0360:     end  .............  |   |         0006:
 0416:   end # of class Foo  | |   |
       <--| missing end here | |   |........ 0347:   def bar
          |                  | |...........  0348:     if @gargle
          |                  |               0349:       puts "glug!"
          |                  |               0350:     #end
          |                  |.............. 0360:   end
          |
          |                                  0415:
          |................................. 0416: end # of class Foo

i think this could be a good ruby quiz/challenge.

kind regards -botp