RE: [Rd] minus: operator and sign (PR#7908)
On 31-May-05 Ted Harding wrote: > [...] > But it is always safe (and often prudent) to force precedence > with parentheses -- at least you yourself are then absolutely > sure of exactly what is going to happen, which is the really > important thing (and this is Rule 2, which takes precedence > over Rule 1). > > So if you want to force "-2^2" and similar to be the square > of "-2" then do "(-2)^2". And it adds clarity to things like > > 2 - - - 2^2 PS: And will also avoid typopathological events such as > x<-y when what you really meant was > x< -y [1] FALSE Ted. E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 31-May-05 Time: 11:50:07 -- XFMail -- __ R-devel@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
RE: [Rd] minus: operator and sign (PR#7908)
On 31-May-05 [EMAIL PROTECTED] wrote: > Full_Name: Allan Sims > Version: 2.1.0 > OS: WinXP > Submission from: (NULL) (193.40.25.254) > > > This should not be correct. It seams that first power is applied and > then sign. >> -2^2 > [1] -4 Rule 1: Know your enemy! ?Syntax --> The following unary and binary operators are defined. They are listed in precedence groups, from highest to lowest. ... '^'exponentiation (right to left) '- +' unary minus and plus ... '+ -' (binary) add, subtract ... So "^" takes precedence over unary "-", which takes precedence over binary "+" and "-". But it is always safe (and often prudent) to force precedence with parentheses -- at least you yourself are then absolutely sure of exactly what is going to happen, which is the really important thing (and this is Rule 2, which takes precedence over Rule 1). So if you want to force "-2^2" and similar to be the square of "-2" then do "(-2)^2". And it adds clarity to things like 2 - - - 2^2 Best wishes, Ted. E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 31-May-05 Time: 11:06:58 -- XFMail -- __ R-devel@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] minus: operator and sign (PR#7908)
Uwe Ligges wrote:
[EMAIL PROTECTED] wrote:
Full_Name: Allan Sims
Version: 2.1.0
OS: WinXP
Submission from: (NULL) (193.40.25.254)
This should not be correct. It seams that first power is applied and
then sign.
-2^2
[1] -4
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So you are telling us in a *bug* report that R works as expected???
The current R Language Definition manual tells us in Section "Parser" -
"Expressions" - "Infox and prefix operators" (which is 10.4.2 in the
current version) the details on the order of precendence ("^" before
unary "-"!).
Please read the docs before submitting bug reports!
Uwe Ligges
BTW: ?Syntax should have told you as well.
Uwe Ligges
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Re: [Rd] minus: operator and sign (PR#7908)
[EMAIL PROTECTED] wrote:
> Full_Name: Allan Sims
> Version: 2.1.0
> OS: WinXP
> Submission from: (NULL) (193.40.25.254)
>
>
> This should not be correct. It seams that first power is applied and then
> sign.
>
>>-2^2
>
> [1] -4
>
> __
> R-devel@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
So you are telling us in a *bug* report that R works as expected???
The current R Language Definition manual tells us in Section "Parser" -
"Expressions" - "Infox and prefix operators" (which is 10.4.2 in the
current version) the details on the order of precendence ("^" before
unary "-"!).
Please read the docs before submitting bug reports!
Uwe Ligges
__
R-devel@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
[Rd] minus: operator and sign (PR#7908)
Full_Name: Allan Sims Version: 2.1.0 OS: WinXP Submission from: (NULL) (193.40.25.254) This should not be correct. It seams that first power is applied and then sign. > -2^2 [1] -4 __ R-devel@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
