[R] Bug(?) in predict.tree() --- Evaluation order of Boolean operators

[David Smith]

> || has higher precedence than & in S (-plus, 6.0 and 3.4), but lower
in R.

Actually, in all versions of S-PLUS (as documented in ?Syntax and
following the Blue Book), ||, |, & and && all have the same precedence
and hence are evaluated left to right.  This explains Christian's
results.

-- 
David M Smith <dsmith at insightful.com>
S-PLUS Product Marketing Manager, Insightful Corp, Seattle WA
Tel: +1 (206) 802 2360
Fax: +1 (206) 283 6310

Insightful Corporation provides analytical solutions leveraging
S-PLUS, StatServer, S-PLUS Analytic Server and consulting services.
See www.insightful.com for details. 

> -----Original Message-----
> From: christian-za.keller at ubs.com [mailto:christian-za.keller at ubs.com]
> Sent: Friday, February 15, 2002 08:32
> To: p.dalgaard at biostat.ku.dk
> Cc: r-help at stat.math.ethz.ch
> Subject: RE: Re: [R] Bug(?) in predict.tree() --- Evaluation order of
> Boolean operators
> 
> 
> Dear Peter 
> 
> Thank you for your help.
> 
> >> It's an operator precedence issue. || has higher 
> precedence than & in
> >> S (-plus, 6.0 and 3.4), but lower in R.
> >>
> >> Try substitute(T||F&F)[[1]]
> >>
> >> I think we want to be compatible, but we'll not likely change it in
> >> the 1.4.x series. However, a set of parentheses should help...
> 
> Note also that in R:
>    > T || F & F
>    [1] TRUE
>    > F & F || T
>    [1] TRUE
>    > substitute(T || F & F)[[1]]
>    ||
>    > substitute(F & F || T)[[1]]
>    ||
> 
> while in S-Plus:
>    > T || F & F
>    [1] F
>    > F & F || T
>    [1] T
>    > substitute(T || F & F)[[1]]
>     & 
>    > substitute(F & F || T)[[1]]
>     || 
> 
> 
> Christian
> 
> ------------------------------------------
> Christian Keller
> ================
> UBS AG
> Analytical CRM UBS CH
> Nüschelerstrasse 22, CH-8098 Zürich
> Tel. +41-1-234 51 48, Fax. +41-1-234 26 83
> christian-za.keller at ubs.com
> 
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