From: Andrew Savige <ajsavige@...>
Date: 2009-03-27T05:03:25+09:00
Subject: Re: Operator precedence of exponentiation (**) and complement (~)


Heesob Park wrote:
> According to the japanese reference
> manual(http://doc.loveruby.net/refm/api/view/spec/operator),
> this is not a bug.
> I guess this precedence change was made on ruby 1.8.0
>
> C:\work\ruby168\bin>ruby -v -e 'p ~2**3'
> ruby 1.6.8 (2002-12-24) [i586-mswin32]
> -9
>
> C:\work\ruby180\bin>ruby -v -e 'p ~2**3'
> ruby 1.8.0 (2003-08-04) [i386-mswin32]
> -27

Thanks. Here's another one that surprised me. Running:

y = 5 % x = 3
print "x=", x, " y=", y, "\n"

produces:

x=3 y=2

That is, it seems that:

y = 5 % x = 3

is being parsed as:

y = 5 % (x = 3)

despite the % operator having a higher precedence than the = operator.
I expected it to be parsed as:

y = (5 % x) = 3

producing a syntax error.

If this is a deliberate feature, I'd be interested in learning more about it.
If anyone knows a good reference on the Ruby parser, please let me know.

Thanks,
/-\



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