On 02/04/2012 11:32, Simen Kjaeraas wrote:
On Mon, 02 Apr 2012 12:03:14 +0200, deadalnix <deadal...@gmail.com> wrote:
I have a design question, or maybe it is a bug ? In D, == and != have the same
precedence than comparisons operators. This isn't the case in C/C++ . Is it a
design
decision, made on purpose ? Is it a bug ?
<snip>
It's there to force proper parenthezation:
<snip>
That combined with associativity rules.
In C(++),
a < b == c <= d
means
(a < b) == (c <= d)
However, if one simply made all the comparison operators equal precedence, then the
meaning of this would change to
((a < b) == c) <= d
However, what has actually been done is to make these operators non-associative as well,
in order to render it an illegal expression. This was done to prevent subtle typos or
confusion with other languages/notations where chaining of comparison operators denotes a
conjunction of the comparisons.
Another way to look at it is that the different comparison operators have no precedence
relative to each other (though each still needs to be non-associative). Indeed, another
change that has taken place is to make the comparison operators have no precedence
relative to the bitwise boolean operators, simply because the C precedence rules here were
confusing.
http://d.puremagic.com/issues/show_bug.cgi?id=4077
Stewart.
