From emil@bode @ending from d@n@@kn@w@nl  Thu Aug 30 16:01:25 2018
From: emil@bode @ending from d@n@@kn@w@nl (Emil Bode)
Date: Thu, 30 Aug 2018 14:01:25 +0000
Subject: [Rd] ROBUSTNESS: x || y and x && y to give warning/error if
 length(x) != 1 or length(y) != 1
In-Reply-To: <CAO1zAVYgQyKP3AbyB_AdTPKogWGQs=cC+YaTtLuG2OSahzvrVA@mail.gmail.com>
References: <CAFDcVCSEqHvfhD358GD3Fgz6FjuOiMiYHswz+pyTnAEoV0CyZw@mail.gmail.com>
 <CAO1zAVaCyKOQLFi2161PB3ycHbr72ue3EtTa189Lz-C+rO1_0w@mail.gmail.com>
 <c5c5721f-65fb-39f0-c7e9-77bb413fbb03@kogentum.hu>
 <CAO1zAVYgQyKP3AbyB_AdTPKogWGQs=cC+YaTtLuG2OSahzvrVA@mail.gmail.com>
Message-ID: <A71C9076-683F-43DE-8DD7-E94F67828806@dans.knaw.nl>

Okay, I thought you always wanted to check the length, but if we can only check what's evaluated I mostly agree.

I still think there's not much wrong with how length-0 logicals are treated, as the return of NA in cases where the value matters is enough warning I think, and I can imagine some code like my previous example 'x==-1 || length(x)==0', which wouldn't need a warning.

But we could do a check for length being >1

Greetings, Emil


?On 30/08/2018, 14:55, "R-devel on behalf of Joris Meys" <r-devel-bounces at r-project.org on behalf of jorismeys at gmail.com> wrote:

    On Thu, Aug 30, 2018 at 2:09 PM D?nes T?th <toth.denes at kogentum.hu> wrote:
    
    > Note that `||` and `&&` have never been symmetric:
    >
    > TRUE || stop() # returns TRUE
    > stop() || TRUE # returns an error
    >
    >
    Fair point. So the suggestion would be to check whether x is of length 1
    and whether y is of length 1 only when needed. I.e.
    
    c(TRUE,FALSE) || TRUE
    
    would give an error and
    
    TRUE || c(TRUE, FALSE)
    
    would pass.
    
    Thought about it a bit more, and I can't come up with a use case where the
    first line must pass. So if the short circuiting remains and the extra
    check only gives a small performance penalty, adding the error could indeed
    make some bugs more obvious.
    
    Cheers
    Joris
    
    -- 
    Joris Meys
    Statistical consultant
    
    Department of Data Analysis and Mathematical Modelling
    Ghent University
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[Rd] ROBUSTNESS: x || y and x && y to give warning/error if length(x) != 1 or length(y) != 1
Emil Bode