Stefano Crocco
8/27/2007 3:27:00 PM
Alle lunedì 27 agosto 2007, Todd Burch ha scritto:
> LOOPER = 6
>
> -(LOOPER).upto(LOOPER) {|i|
> puts i }
>
> I get one line of output: 6
>
> However, I get 13 lines of output here:
>
> (-LOOPER).upto(LOOPER) {|i|
> puts i }
>
> What is happening with the unary minus on the first example? I expected
> to get identical output.
>
> Todd
I'm not completely sure, but I think the difference arises because of operator
precedence. The first expression is interpreted as
-(LOOPER.upto(LOOPER){|i| puts i})
Since the lower and upper bounds are equal, the iteration is performed only
one time. The - is then applied to the return value of upto (the receiver,
i.e LOOPER). Indeed, if you try your code in irb, you'll see that the value
of the expression is -6.
In the second case, using brackets you tell the interpreter that the upto
method should not be called on LOOPER, but on (-LOOPER), that is on -6.
I hope this helps
Stefano