New Operator

Lars T Hansen lth at acm.org
Thu Mar 6 06:08:20 PST 2008


Tucker,

I detect sarcasm in your reply, but maybe I'm just being paranoid now...

R4RS Scheme:

"For integers n1 and n2 with n2 not equal to 0,

(= n1 (+ (* n2 (quotient n1 n2))  (remainder n1 n2)))"


E262-3 (the % operator):

"In the remaining cases, where neither an infinity, nor a zero, nor
NaN is involved, the floating-point remainder r from a dividend n and
a divisor d is defined by the mathematical relation r = n − (d * q)
where q is an integer that is negative only if n/d is negative and
positive only if n/d is positive, and whose magnitude is as large as
possible without exceeding the magnitude of the true mathematical
quotient of n and d."

Div truncates and the definition is machine independent and
complements that of  %.

Since / rounds (among other operators) but there is no way to control
its rounding mode, I don't know why 'div' should have that control
either, necessarily.

--lars

On 3/6/08, P T Withington <ptw at pobox.com> wrote:
> Don't you want to be able to express rounding mode?  And if so, do you
>  need 4 operators? floor/, ceiling/, round/, truncate/?  Oh, maybe they
>  should be named /-, /+, /~ and /0.  Yow.
>
>  Is div truncate/, or round/?  I can never remember.
>
>
>  On 2008-03-05, at 18:18 EST, Lars Hansen wrote:
>
>  > Just \ would work if we're happy with not allowing its use at the
>  > end of
>  > a line.  A little dodgy, syntactically, IMO.  I've advocated "\\" in
>  > the
>  > past, which by normal lexing rules would be unambiguous by the
>  > longest-token lexing rule.
>  >
>  > ("/." is ambiguous, consider 3/.5.)
>  >
>  > --lars
>  >
>  >
>  > ________________________________
>  >
>  >       From: Michael O'Brien [mailto:mob at mbedthis.com]
>  >       Sent: 5. mars 2008 15:06
>  >       To: Lars Hansen
>  >       Cc: TNO; es4-discuss at mozilla.org
>  >       Subject: Re: New Operator
>  >
>  >
>  >       I'll vote for that also. It improves readability quite a bit.
>  >
>  >       But is there a better operator than "\"?
>  >
>  >       Shame "//" is taken.  What about  "/."
>  >
>  >       Michael
>  >
>  >       Lars Hansen wrote:
>  >
>  >               I have been pushing for this in the past on several
>  > occasions, but enthusiasm in the WG has been scant, unfortunately.
>  > Maybe I haven't been pushing hard enough.
>  >
>  >               --lars
>  >
>  >
>  > ________________________________
>  >
>  >                       From: es4-discuss-bounces at mozilla.org
>  > [mailto:es4-discuss-bounces at mozilla.org] On Behalf Of TNO
>  >                       Sent: 5. mars 2008 14:13
>  >                       To: es4-discuss at mozilla.org
>  >                       Subject: New Operator
>  >
>  >
>  >                       Is it too late to propose an integer division
>  > operator into the spec? I do quite a bit of WSH programming in both
>  > VBScript an JScript and sometimes its a bit of an irritant during a
>  > translation, it would be nice to see this operator "\" available in
>  > the
>  > new ECMAScript instead of having to rely on more inefficient
>  > workarounds:
>  >
>  >                       VBScript:
>  >
>  >                       Dim result
>  >                       result = 19 \ 4 '(result = 4)
>  >
>  >                       JScript:
>  >
>  > http://www.codingforums.com/showthread.php?t=58799
>  >
>  >
>  > ________________________________
>  >
>  >
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>  >               Es4-discuss at mozilla.org
>  >               https://mail.mozilla.org/listinfo/es4-discuss
>  >
>  >
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