From: Joel VanderWerf <vjoel@...>
Date: 2004-04-22T04:37:25+09:00
Subject: Re: TCLTK didn't work with do ... end ??

Daniel Bovensiepen [bovi] wrote:
...
>   command proc {
>     puts 'klick'
>   }
...
> why didn't work the 'command proc' with a do ... end?
...
>   command proc do
>     puts 'klick'
>   end

It's because of precedence. In the first case, the {...} is associated 
with 'proc'. In the second case, it is associated with 'command'. This 
may show it more clearly:

def foo(*args, &bl)
   puts "In foo: got args == #{args.inspect}"
   puts "In foo: got block == #{bl.inspect}"
end

def bar(*args, &bl)
   puts "In bar: got args == #{args.inspect}"
   puts "In bar: got block == #{bl.inspect}"
end

foo bar {}

foo bar do end

-- output --
In bar: got args == []
In bar: got block == #<Proc:0x00000000@-:11>
In foo: got args == [nil]
In foo: got block == nil
In bar: got args == []
In bar: got block == nil
In foo: got args == [nil]
In foo: got block == #<Proc:0x00000000@-:13>