Hello,
I heard we can override almost everything in R. Is it possible to override "if" keyword in R to evaluate my own object instead of a logical value? Thanks, Da ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
You can. Perhaps needless to say, be careful with this.
❯ `if` <- function(...) FALSE ❯ if (TRUE) TRUE else FALSE [1] FALSE G. On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> wrote: > Hello, > > I heard we can override almost everything in R. Is it possible to > override "if" keyword in R to evaluate my own object instead of a > logical value? > > Thanks, > Da > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Thanks.
Can I override it for a specific class? I can do that for operators such as "!". For example, "!.fm" works for objects of the class "fm". It seems I can't do the same for "if". Best, Da On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi <[hidden email]> wrote: > You can. Perhaps needless to say, be careful with this. > > ❯ `if` <- function(...) FALSE > ❯ if (TRUE) TRUE else FALSE > [1] FALSE > > G. > > On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> wrote: >> Hello, >> >> I heard we can override almost everything in R. Is it possible to >> override "if" keyword in R to evaluate my own object instead of a >> logical value? >> >> Thanks, >> Da >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
`!` is a generic, `if` is not. You can define an `if` that is generic,
but this might be even more dangerous.... ❯ `if` <- function(a, b, c) UseMethod("if") ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) ❯ `if.foo` <- function(a, b, c) FALSE ❯ a <- structure(42, class = "foo") ❯ if (a) TRUE else FALSE [1] FALSE ❯ if (1) TRUE else FALSE [1] TRUE Gabor On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> wrote: > Thanks. > Can I override it for a specific class? > I can do that for operators such as "!". For example, "!.fm" works for > objects of the class "fm". > It seems I can't do the same for "if". > > Best, > Da > > On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi <[hidden email]> wrote: >> You can. Perhaps needless to say, be careful with this. >> >> ❯ `if` <- function(...) FALSE >> ❯ if (TRUE) TRUE else FALSE >> [1] FALSE >> >> G. >> >> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> wrote: >>> Hello, >>> >>> I heard we can override almost everything in R. Is it possible to >>> override "if" keyword in R to evaluate my own object instead of a >>> logical value? >>> >>> Thanks, >>> Da >>> >>> ______________________________________________ >>> [hidden email] mailing list >>> https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
I'm just curious. Why making "if" generic is even more dangerous?
Best, Da On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email]> wrote: > `!` is a generic, `if` is not. You can define an `if` that is generic, > but this might be even more dangerous.... > > ❯ `if` <- function(a, b, c) UseMethod("if") > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) > ❯ `if.foo` <- function(a, b, c) FALSE > ❯ a <- structure(42, class = "foo") > > ❯ if (a) TRUE else FALSE > [1] FALSE > > ❯ if (1) TRUE else FALSE > [1] TRUE > > Gabor > > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> wrote: >> Thanks. >> Can I override it for a specific class? >> I can do that for operators such as "!". For example, "!.fm" works for >> objects of the class "fm". >> It seems I can't do the same for "if". >> >> Best, >> Da >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi <[hidden email]> wrote: >>> You can. Perhaps needless to say, be careful with this. >>> >>> ❯ `if` <- function(...) FALSE >>> ❯ if (TRUE) TRUE else FALSE >>> [1] FALSE >>> >>> G. >>> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> wrote: >>>> Hello, >>>> >>>> I heard we can override almost everything in R. Is it possible to >>>> override "if" keyword in R to evaluate my own object instead of a >>>> logical value? >>>> >>>> Thanks, >>>> Da >>>> >>>> ______________________________________________ >>>> [hidden email] mailing list >>>> https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
I'm curious as to precisely why someone would want to do this.
On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> wrote: > I'm just curious. Why making "if" generic is even more dangerous? > > Best, > Da > > On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email]> > wrote: > > `!` is a generic, `if` is not. You can define an `if` that is generic, > > but this might be even more dangerous.... > > > > ❯ `if` <- function(a, b, c) UseMethod("if") > > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) > > ❯ `if.foo` <- function(a, b, c) FALSE > > ❯ a <- structure(42, class = "foo") > > > > ❯ if (a) TRUE else FALSE > > [1] FALSE > > > > ❯ if (1) TRUE else FALSE > > [1] TRUE > > > > Gabor > > > > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> wrote: > >> Thanks. > >> Can I override it for a specific class? > >> I can do that for operators such as "!". For example, "!.fm" works for > >> objects of the class "fm". > >> It seems I can't do the same for "if". > >> > >> Best, > >> Da > >> > >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi <[hidden email]> > wrote: > >>> You can. Perhaps needless to say, be careful with this. > >>> > >>> ❯ `if` <- function(...) FALSE > >>> ❯ if (TRUE) TRUE else FALSE > >>> [1] FALSE > >>> > >>> G. > >>> > >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> > wrote: > >>>> Hello, > >>>> > >>>> I heard we can override almost everything in R. Is it possible to > >>>> override "if" keyword in R to evaluate my own object instead of a > >>>> logical value? > >>>> > >>>> Thanks, > >>>> Da > >>>> > >>>> ______________________________________________ > >>>> [hidden email] mailing list > >>>> https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
In my case, I create a new type of matrices and override matrix
operations in R for these matrices. My goal is to make the system as transparent as possible, which means my system should execute the existing R code without modification. The problem is that when data is in my own vectors or matrices, "if" or "while" can't access their values unless we explicitly convert them into R objects. But this means users need to modify the existing code. So I hope I can override "if", "while", etc to access data in my own vectors and matrices directly. Does this sound reasonable? Best, Da On Sat, Mar 4, 2017 at 3:22 PM, Michael Lawrence <[hidden email]> wrote: > I'm curious as to precisely why someone would want to do this. > > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> wrote: >> >> I'm just curious. Why making "if" generic is even more dangerous? >> >> Best, >> Da >> >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email]> >> wrote: >> > `!` is a generic, `if` is not. You can define an `if` that is generic, >> > but this might be even more dangerous.... >> > >> > ❯ `if` <- function(a, b, c) UseMethod("if") >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) >> > ❯ `if.foo` <- function(a, b, c) FALSE >> > ❯ a <- structure(42, class = "foo") >> > >> > ❯ if (a) TRUE else FALSE >> > [1] FALSE >> > >> > ❯ if (1) TRUE else FALSE >> > [1] TRUE >> > >> > Gabor >> > >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> wrote: >> >> Thanks. >> >> Can I override it for a specific class? >> >> I can do that for operators such as "!". For example, "!.fm" works for >> >> objects of the class "fm". >> >> It seems I can't do the same for "if". >> >> >> >> Best, >> >> Da >> >> >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi <[hidden email]> >> >> wrote: >> >>> You can. Perhaps needless to say, be careful with this. >> >>> >> >>> ❯ `if` <- function(...) FALSE >> >>> ❯ if (TRUE) TRUE else FALSE >> >>> [1] FALSE >> >>> >> >>> G. >> >>> >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> >> >>> wrote: >> >>>> Hello, >> >>>> >> >>>> I heard we can override almost everything in R. Is it possible to >> >>>> override "if" keyword in R to evaluate my own object instead of a >> >>>> logical value? >> >>>> >> >>>> Thanks, >> >>>> Da >> >>>> >> >>>> ______________________________________________ >> >>>> [hidden email] mailing list >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
In reply to this post by Michael Lawrence-3
dplyr::translate_sql() redefines lots of functions, include "if", to
translate from R syntax to SQL syntax. > dplyr::translate_sql(if ("mpg">25) "better" else "worse") <SQL> CASE WHEN ('mpg' > 25.0) THEN ('better') ELSE ('worse') END Bill Dunlap TIBCO Software wdunlap tibco.com On Sat, Mar 4, 2017 at 12:22 PM, Michael Lawrence <[hidden email]> wrote: > I'm curious as to precisely why someone would want to do this. > > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> wrote: > >> I'm just curious. Why making "if" generic is even more dangerous? >> >> Best, >> Da >> >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email]> >> wrote: >> > `!` is a generic, `if` is not. You can define an `if` that is generic, >> > but this might be even more dangerous.... >> > >> > ❯ `if` <- function(a, b, c) UseMethod("if") >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) >> > ❯ `if.foo` <- function(a, b, c) FALSE >> > ❯ a <- structure(42, class = "foo") >> > >> > ❯ if (a) TRUE else FALSE >> > [1] FALSE >> > >> > ❯ if (1) TRUE else FALSE >> > [1] TRUE >> > >> > Gabor >> > >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> wrote: >> >> Thanks. >> >> Can I override it for a specific class? >> >> I can do that for operators such as "!". For example, "!.fm" works for >> >> objects of the class "fm". >> >> It seems I can't do the same for "if". >> >> >> >> Best, >> >> Da >> >> >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi <[hidden email]> >> wrote: >> >>> You can. Perhaps needless to say, be careful with this. >> >>> >> >>> ❯ `if` <- function(...) FALSE >> >>> ❯ if (TRUE) TRUE else FALSE >> >>> [1] FALSE >> >>> >> >>> G. >> >>> >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> >> wrote: >> >>>> Hello, >> >>>> >> >>>> I heard we can override almost everything in R. Is it possible to >> >>>> override "if" keyword in R to evaluate my own object instead of a >> >>>> logical value? >> >>>> >> >>>> Thanks, >> >>>> Da >> >>>> >> >>>> ______________________________________________ >> >>>> [hidden email] mailing list >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
In reply to this post by Da Zheng
Because the S3 class system is very informal. E.g. if you happen to
have an `if.whatever` function, that will be automatically a method of your generic. Gabor On Sat, Mar 4, 2017 at 7:49 PM, Da Zheng <[hidden email]> wrote: > I'm just curious. Why making "if" generic is even more dangerous? > > Best, > Da > > On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email]> wrote: >> `!` is a generic, `if` is not. You can define an `if` that is generic, >> but this might be even more dangerous.... >> >> ❯ `if` <- function(a, b, c) UseMethod("if") >> ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) >> ❯ `if.foo` <- function(a, b, c) FALSE >> ❯ a <- structure(42, class = "foo") >> >> ❯ if (a) TRUE else FALSE >> [1] FALSE >> >> ❯ if (1) TRUE else FALSE >> [1] TRUE >> >> Gabor >> >> On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> wrote: >>> Thanks. >>> Can I override it for a specific class? >>> I can do that for operators such as "!". For example, "!.fm" works for >>> objects of the class "fm". >>> It seems I can't do the same for "if". >>> >>> Best, >>> Da >>> >>> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi <[hidden email]> wrote: >>>> You can. Perhaps needless to say, be careful with this. >>>> >>>> ❯ `if` <- function(...) FALSE >>>> ❯ if (TRUE) TRUE else FALSE >>>> [1] FALSE >>>> >>>> G. >>>> >>>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> wrote: >>>>> Hello, >>>>> >>>>> I heard we can override almost everything in R. Is it possible to >>>>> override "if" keyword in R to evaluate my own object instead of a >>>>> logical value? >>>>> >>>>> Thanks, >>>>> Da >>>>> >>>>> ______________________________________________ >>>>> [hidden email] mailing list >>>>> https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
On Sun, Mar 5, 2017 at 8:13 PM, Gábor Csárdi <[hidden email]> wrote:
> Because the S3 class system is very informal. E.g. if you happen to > have an `if.whatever` function, that will be automatically a method of > your generic. For example: x <- structure(1:10, class = "test") t(x) #> #> One Sample t-test #> #> data: x #> t = 5.7446, df = 9, p-value = 0.0002782 #> alternative hypothesis: true mean is not equal to 0 #> 95 percent confidence interval: #> 3.334149 7.665851 #> sample estimates: #> mean of x #> 5.5 -- http://hadley.nz ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
In reply to this post by Da Zheng
On Sat, Mar 4, 2017 at 12:36 PM, Da Zheng <[hidden email]> wrote:
> In my case, I create a new type of matrices and override matrix > operations in R for these matrices. > My goal is to make the system as transparent as possible, which means > my system should execute the existing R code without modification. > The problem is that when data is in my own vectors or matrices, "if" > or "while" can't access their values unless we explicitly convert them > into R objects. But this means users need to modify the existing code. > So I hope I can override "if", "while", etc to access data in my own > vectors and matrices directly. > Does this sound reasonable? > > I can see a case in the deferred evaluation context, although it would be problematic wrt side effects unless the deferral is complete. > Best, > Da > > On Sat, Mar 4, 2017 at 3:22 PM, Michael Lawrence > <[hidden email]> wrote: > > I'm curious as to precisely why someone would want to do this. > > > > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> wrote: > >> > >> I'm just curious. Why making "if" generic is even more dangerous? > >> > >> Best, > >> Da > >> > >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email]> > >> wrote: > >> > `!` is a generic, `if` is not. You can define an `if` that is generic, > >> > but this might be even more dangerous.... > >> > > >> > ❯ `if` <- function(a, b, c) UseMethod("if") > >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) > >> > ❯ `if.foo` <- function(a, b, c) FALSE > >> > ❯ a <- structure(42, class = "foo") > >> > > >> > ❯ if (a) TRUE else FALSE > >> > [1] FALSE > >> > > >> > ❯ if (1) TRUE else FALSE > >> > [1] TRUE > >> > > >> > Gabor > >> > > >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> > wrote: > >> >> Thanks. > >> >> Can I override it for a specific class? > >> >> I can do that for operators such as "!". For example, "!.fm" works > for > >> >> objects of the class "fm". > >> >> It seems I can't do the same for "if". > >> >> > >> >> Best, > >> >> Da > >> >> > >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi < > [hidden email]> > >> >> wrote: > >> >>> You can. Perhaps needless to say, be careful with this. > >> >>> > >> >>> ❯ `if` <- function(...) FALSE > >> >>> ❯ if (TRUE) TRUE else FALSE > >> >>> [1] FALSE > >> >>> > >> >>> G. > >> >>> > >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> > >> >>> wrote: > >> >>>> Hello, > >> >>>> > >> >>>> I heard we can override almost everything in R. Is it possible to > >> >>>> override "if" keyword in R to evaluate my own object instead of a > >> >>>> logical value? > >> >>>> > >> >>>> Thanks, > >> >>>> Da > >> >>>> > >> >>>> ______________________________________________ > >> >>>> [hidden email] mailing list > >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel > >> > >> ______________________________________________ > >> [hidden email] mailing list > >> https://stat.ethz.ch/mailman/listinfo/r-devel > > > > > [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
On Sun, Mar 5, 2017 at 2:50 PM, Michael Lawrence
<[hidden email]> wrote: > > > On Sat, Mar 4, 2017 at 12:36 PM, Da Zheng <[hidden email]> wrote: >> >> In my case, I create a new type of matrices and override matrix >> operations in R for these matrices. >> My goal is to make the system as transparent as possible, which means >> my system should execute the existing R code without modification. >> The problem is that when data is in my own vectors or matrices, "if" >> or "while" can't access their values unless we explicitly convert them >> into R objects. But this means users need to modify the existing code. >> So I hope I can override "if", "while", etc to access data in my own >> vectors and matrices directly. >> Does this sound reasonable? >> > > Would you really need the alternate representation for scalar logicals? > > I can see a case in the deferred evaluation context, although it would be > problematic wrt side effects unless the deferral is complete. "if" for the matrices. In my framework, all matrices are read-only, so there isn't side effect. Best, Da > > > >> >> Best, >> Da >> >> On Sat, Mar 4, 2017 at 3:22 PM, Michael Lawrence >> <[hidden email]> wrote: >> > I'm curious as to precisely why someone would want to do this. >> > >> > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> wrote: >> >> >> >> I'm just curious. Why making "if" generic is even more dangerous? >> >> >> >> Best, >> >> Da >> >> >> >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email]> >> >> wrote: >> >> > `!` is a generic, `if` is not. You can define an `if` that is >> >> > generic, >> >> > but this might be even more dangerous.... >> >> > >> >> > ❯ `if` <- function(a, b, c) UseMethod("if") >> >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) >> >> > ❯ `if.foo` <- function(a, b, c) FALSE >> >> > ❯ a <- structure(42, class = "foo") >> >> > >> >> > ❯ if (a) TRUE else FALSE >> >> > [1] FALSE >> >> > >> >> > ❯ if (1) TRUE else FALSE >> >> > [1] TRUE >> >> > >> >> > Gabor >> >> > >> >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> >> >> > wrote: >> >> >> Thanks. >> >> >> Can I override it for a specific class? >> >> >> I can do that for operators such as "!". For example, "!.fm" works >> >> >> for >> >> >> objects of the class "fm". >> >> >> It seems I can't do the same for "if". >> >> >> >> >> >> Best, >> >> >> Da >> >> >> >> >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi >> >> >> <[hidden email]> >> >> >> wrote: >> >> >>> You can. Perhaps needless to say, be careful with this. >> >> >>> >> >> >>> ❯ `if` <- function(...) FALSE >> >> >>> ❯ if (TRUE) TRUE else FALSE >> >> >>> [1] FALSE >> >> >>> >> >> >>> G. >> >> >>> >> >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> >> >> >>> wrote: >> >> >>>> Hello, >> >> >>>> >> >> >>>> I heard we can override almost everything in R. Is it possible to >> >> >>>> override "if" keyword in R to evaluate my own object instead of a >> >> >>>> logical value? >> >> >>>> >> >> >>>> Thanks, >> >> >>>> Da >> >> >>>> >> >> >>>> ______________________________________________ >> >> >>>> [hidden email] mailing list >> >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> >> >> ______________________________________________ >> >> [hidden email] mailing list >> >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > >> > > > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Da,
I've been following this thread and I'm still confused as to exactly what you want/why you want it. I'm probably just missing some context here, but, If() doesn't operate on matrices, generally. Can you give an example of the type of code you want to have continue to run that requires if operation *directly* on one of your matrix objects, as opposed, say, to a value pulled out from it, or the dot-product of two vectors in your system, both of which would be values (scalars) not matrices. Now ifelse(), is of course, a different beast altogether, and would need to be overloaded within your system, I imagine. Best, ~G On Sun, Mar 5, 2017 at 12:52 PM, Da Zheng <[hidden email]> wrote: > On Sun, Mar 5, 2017 at 2:50 PM, Michael Lawrence > <[hidden email]> wrote: > > > > > > On Sat, Mar 4, 2017 at 12:36 PM, Da Zheng <[hidden email]> wrote: > >> > >> In my case, I create a new type of matrices and override matrix > >> operations in R for these matrices. > >> My goal is to make the system as transparent as possible, which means > >> my system should execute the existing R code without modification. > >> The problem is that when data is in my own vectors or matrices, "if" > >> or "while" can't access their values unless we explicitly convert them > >> into R objects. But this means users need to modify the existing code. > >> So I hope I can override "if", "while", etc to access data in my own > >> vectors and matrices directly. > >> Does this sound reasonable? > >> > > > > Would you really need the alternate representation for scalar logicals? > > > > I can see a case in the deferred evaluation context, although it would be > > problematic wrt side effects unless the deferral is complete. > This is exactly why I want to use my own matrix objects and redefine > "if" for the matrices. In my framework, all matrices are read-only, so > there isn't side effect. > > Best, > Da > > > > > > > >> > >> Best, > >> Da > >> > >> On Sat, Mar 4, 2017 at 3:22 PM, Michael Lawrence > >> <[hidden email]> wrote: > >> > I'm curious as to precisely why someone would want to do this. > >> > > >> > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> > wrote: > >> >> > >> >> I'm just curious. Why making "if" generic is even more dangerous? > >> >> > >> >> Best, > >> >> Da > >> >> > >> >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email] > > > >> >> wrote: > >> >> > `!` is a generic, `if` is not. You can define an `if` that is > >> >> > generic, > >> >> > but this might be even more dangerous.... > >> >> > > >> >> > ❯ `if` <- function(a, b, c) UseMethod("if") > >> >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) > >> >> > ❯ `if.foo` <- function(a, b, c) FALSE > >> >> > ❯ a <- structure(42, class = "foo") > >> >> > > >> >> > ❯ if (a) TRUE else FALSE > >> >> > [1] FALSE > >> >> > > >> >> > ❯ if (1) TRUE else FALSE > >> >> > [1] TRUE > >> >> > > >> >> > Gabor > >> >> > > >> >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> > >> >> > wrote: > >> >> >> Thanks. > >> >> >> Can I override it for a specific class? > >> >> >> I can do that for operators such as "!". For example, "!.fm" works > >> >> >> for > >> >> >> objects of the class "fm". > >> >> >> It seems I can't do the same for "if". > >> >> >> > >> >> >> Best, > >> >> >> Da > >> >> >> > >> >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi > >> >> >> <[hidden email]> > >> >> >> wrote: > >> >> >>> You can. Perhaps needless to say, be careful with this. > >> >> >>> > >> >> >>> ❯ `if` <- function(...) FALSE > >> >> >>> ❯ if (TRUE) TRUE else FALSE > >> >> >>> [1] FALSE > >> >> >>> > >> >> >>> G. > >> >> >>> > >> >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> > >> >> >>> wrote: > >> >> >>>> Hello, > >> >> >>>> > >> >> >>>> I heard we can override almost everything in R. Is it possible > to > >> >> >>>> override "if" keyword in R to evaluate my own object instead of > a > >> >> >>>> logical value? > >> >> >>>> > >> >> >>>> Thanks, > >> >> >>>> Da > >> >> >>>> > >> >> >>>> ______________________________________________ > >> >> >>>> [hidden email] mailing list > >> >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel > >> >> > >> >> ______________________________________________ > >> >> [hidden email] mailing list > >> >> https://stat.ethz.ch/mailman/listinfo/r-devel > >> > > >> > > > > > > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- Gabriel Becker, PhD Associate Scientist (Bioinformatics) Genentech Research [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
I can't comment for Da, but one example where the ability to make 'if' generic would have been desirable:
A couple of years ago I wrote S3 classes and methods for 1-byte integers and logicals stored as raw vectors, in order to handle massive amounts of genetic data (by the standards of the day). Everything worked pretty nicely, ie I could "methodize" just about everything I needed--- except if-statements, which would fail to respect eg my definitions of NA. [ The precise details elude me, but if() was untrustworthy. ] To use 'if()', I had to remember to "typecast", which was prone to "user error". Whether this kind of thing is worth the "risk", is another matter. cheers Mark Mark Bravington CSIRO Marine Lab Hobart Australia ________________________________________ From: R-devel [[hidden email]] on behalf of Gabriel Becker [[hidden email]] Sent: 06 March 2017 11:43 To: Da Zheng Cc: [hidden email] Subject: Re: [Rd] can we override "if" in R? Da, I've been following this thread and I'm still confused as to exactly what you want/why you want it. I'm probably just missing some context here, but, If() doesn't operate on matrices, generally. Can you give an example of the type of code you want to have continue to run that requires if operation *directly* on one of your matrix objects, as opposed, say, to a value pulled out from it, or the dot-product of two vectors in your system, both of which would be values (scalars) not matrices. Now ifelse(), is of course, a different beast altogether, and would need to be overloaded within your system, I imagine. Best, ~G On Sun, Mar 5, 2017 at 12:52 PM, Da Zheng <[hidden email]> wrote: > On Sun, Mar 5, 2017 at 2:50 PM, Michael Lawrence > <[hidden email]> wrote: > > > > > > On Sat, Mar 4, 2017 at 12:36 PM, Da Zheng <[hidden email]> wrote: > >> > >> In my case, I create a new type of matrices and override matrix > >> operations in R for these matrices. > >> My goal is to make the system as transparent as possible, which means > >> my system should execute the existing R code without modification. > >> The problem is that when data is in my own vectors or matrices, "if" > >> or "while" can't access their values unless we explicitly convert them > >> into R objects. But this means users need to modify the existing code. > >> So I hope I can override "if", "while", etc to access data in my own > >> vectors and matrices directly. > >> Does this sound reasonable? > >> > > > > Would you really need the alternate representation for scalar logicals? > > > > I can see a case in the deferred evaluation context, although it would be > > problematic wrt side effects unless the deferral is complete. > This is exactly why I want to use my own matrix objects and redefine > "if" for the matrices. In my framework, all matrices are read-only, so > there isn't side effect. > > Best, > Da > > > > > > > >> > >> Best, > >> Da > >> > >> On Sat, Mar 4, 2017 at 3:22 PM, Michael Lawrence > >> <[hidden email]> wrote: > >> > I'm curious as to precisely why someone would want to do this. > >> > > >> > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> > wrote: > >> >> > >> >> I'm just curious. Why making "if" generic is even more dangerous? > >> >> > >> >> Best, > >> >> Da > >> >> > >> >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email] > > > >> >> wrote: > >> >> > `!` is a generic, `if` is not. You can define an `if` that is > >> >> > generic, > >> >> > but this might be even more dangerous.... > >> >> > > >> >> > ❯ `if` <- function(a, b, c) UseMethod("if") > >> >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) > >> >> > ❯ `if.foo` <- function(a, b, c) FALSE > >> >> > ❯ a <- structure(42, class = "foo") > >> >> > > >> >> > ❯ if (a) TRUE else FALSE > >> >> > [1] FALSE > >> >> > > >> >> > ❯ if (1) TRUE else FALSE > >> >> > [1] TRUE > >> >> > > >> >> > Gabor > >> >> > > >> >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> > >> >> > wrote: > >> >> >> Thanks. > >> >> >> Can I override it for a specific class? > >> >> >> I can do that for operators such as "!". For example, "!.fm" works > >> >> >> for > >> >> >> objects of the class "fm". > >> >> >> It seems I can't do the same for "if". > >> >> >> > >> >> >> Best, > >> >> >> Da > >> >> >> > >> >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi > >> >> >> <[hidden email]> > >> >> >> wrote: > >> >> >>> You can. Perhaps needless to say, be careful with this. > >> >> >>> > >> >> >>> ❯ `if` <- function(...) FALSE > >> >> >>> ❯ if (TRUE) TRUE else FALSE > >> >> >>> [1] FALSE > >> >> >>> > >> >> >>> G. > >> >> >>> > >> >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> > >> >> >>> wrote: > >> >> >>>> Hello, > >> >> >>>> > >> >> >>>> I heard we can override almost everything in R. Is it possible > to > >> >> >>>> override "if" keyword in R to evaluate my own object instead of > a > >> >> >>>> logical value? > >> >> >>>> > >> >> >>>> Thanks, > >> >> >>>> Da > >> >> >>>> > >> >> >>>> ______________________________________________ > >> >> >>>> [hidden email] mailing list > >> >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel > >> >> > >> >> ______________________________________________ > >> >> [hidden email] mailing list > >> >> https://stat.ethz.ch/mailman/listinfo/r-devel > >> > > >> > > > > > > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- Gabriel Becker, PhD Associate Scientist (Bioinformatics) Genentech Research [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
In reply to this post by Gabriel Becker
Da Zheng would like to override 'if' and 'while' to accept more than
scalar logicals and Martin Maechler would like to change 'if' to accept only scalar logicals. No one has mentioned '||' and '&&', which also want scalar logicals. Perhaps a solution is to have all of these call a new generic function, as.scalar.logical() on their relevant arguments. (For efficiency, the default would be internally dispatched). Bill Dunlap TIBCO Software wdunlap tibco.com On Sun, Mar 5, 2017 at 4:43 PM, Gabriel Becker <[hidden email]> wrote: > Da, > > I've been following this thread and I'm still confused as to exactly what > you want/why you want it. > > I'm probably just missing some context here, but, If() doesn't operate on > matrices, generally. Can you give an example of the type of code you want > to have continue to run that requires if operation *directly* on one of > your matrix objects, as opposed, say, to a value pulled out from it, or the > dot-product of two vectors in your system, both of which would be values > (scalars) not matrices. > > Now ifelse(), is of course, a different beast altogether, and would need to > be overloaded within your system, I imagine. > > Best, > ~G > > On Sun, Mar 5, 2017 at 12:52 PM, Da Zheng <[hidden email]> wrote: > >> On Sun, Mar 5, 2017 at 2:50 PM, Michael Lawrence >> <[hidden email]> wrote: >> > >> > >> > On Sat, Mar 4, 2017 at 12:36 PM, Da Zheng <[hidden email]> wrote: >> >> >> >> In my case, I create a new type of matrices and override matrix >> >> operations in R for these matrices. >> >> My goal is to make the system as transparent as possible, which means >> >> my system should execute the existing R code without modification. >> >> The problem is that when data is in my own vectors or matrices, "if" >> >> or "while" can't access their values unless we explicitly convert them >> >> into R objects. But this means users need to modify the existing code. >> >> So I hope I can override "if", "while", etc to access data in my own >> >> vectors and matrices directly. >> >> Does this sound reasonable? >> >> >> > >> > Would you really need the alternate representation for scalar logicals? >> > >> > I can see a case in the deferred evaluation context, although it would be >> > problematic wrt side effects unless the deferral is complete. >> This is exactly why I want to use my own matrix objects and redefine >> "if" for the matrices. In my framework, all matrices are read-only, so >> there isn't side effect. >> >> Best, >> Da >> > >> > >> > >> >> >> >> Best, >> >> Da >> >> >> >> On Sat, Mar 4, 2017 at 3:22 PM, Michael Lawrence >> >> <[hidden email]> wrote: >> >> > I'm curious as to precisely why someone would want to do this. >> >> > >> >> > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> >> wrote: >> >> >> >> >> >> I'm just curious. Why making "if" generic is even more dangerous? >> >> >> >> >> >> Best, >> >> >> Da >> >> >> >> >> >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi <[hidden email] >> > >> >> >> wrote: >> >> >> > `!` is a generic, `if` is not. You can define an `if` that is >> >> >> > generic, >> >> >> > but this might be even more dangerous.... >> >> >> > >> >> >> > ❯ `if` <- function(a, b, c) UseMethod("if") >> >> >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) >> >> >> > ❯ `if.foo` <- function(a, b, c) FALSE >> >> >> > ❯ a <- structure(42, class = "foo") >> >> >> > >> >> >> > ❯ if (a) TRUE else FALSE >> >> >> > [1] FALSE >> >> >> > >> >> >> > ❯ if (1) TRUE else FALSE >> >> >> > [1] TRUE >> >> >> > >> >> >> > Gabor >> >> >> > >> >> >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> >> >> >> > wrote: >> >> >> >> Thanks. >> >> >> >> Can I override it for a specific class? >> >> >> >> I can do that for operators such as "!". For example, "!.fm" works >> >> >> >> for >> >> >> >> objects of the class "fm". >> >> >> >> It seems I can't do the same for "if". >> >> >> >> >> >> >> >> Best, >> >> >> >> Da >> >> >> >> >> >> >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi >> >> >> >> <[hidden email]> >> >> >> >> wrote: >> >> >> >>> You can. Perhaps needless to say, be careful with this. >> >> >> >>> >> >> >> >>> ❯ `if` <- function(...) FALSE >> >> >> >>> ❯ if (TRUE) TRUE else FALSE >> >> >> >>> [1] FALSE >> >> >> >>> >> >> >> >>> G. >> >> >> >>> >> >> >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng <[hidden email]> >> >> >> >>> wrote: >> >> >> >>>> Hello, >> >> >> >>>> >> >> >> >>>> I heard we can override almost everything in R. Is it possible >> to >> >> >> >>>> override "if" keyword in R to evaluate my own object instead of >> a >> >> >> >>>> logical value? >> >> >> >>>> >> >> >> >>>> Thanks, >> >> >> >>>> Da >> >> >> >>>> >> >> >> >>>> ______________________________________________ >> >> >> >>>> [hidden email] mailing list >> >> >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> >> >> >> >> ______________________________________________ >> >> >> [hidden email] mailing list >> >> >> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> > >> >> > >> > >> > >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > > > > -- > Gabriel Becker, PhD > Associate Scientist (Bioinformatics) > Genentech Research > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
In reply to this post by Mark.Bravington
Mark,
I do understand this desire, though notably, if selecting a single element from one of these custom vectors gave you a normal value, if would be safe, right? e.g. if the [ method, etc checked if the index length is one, and returned the non-compressed value if it was, as an off-the-cuff possibility. Also, I do feel compelled to say that I'm working with R-core (Luke Tierney primarily) on low-level support for this kind of data-storage abstraction that would let you create custom vector/matrix storage mechanisms that still behave themselves as atomic vectors. See https://www.r-project.org/dsc/2016/slides/customvectors.html for my initial pitch and https://svn.r-project.org/R/branches/ALTREP/ <https://svn.r-project.org/R/branches/ALTREP/> for the work-in-progress branch. We hope to merge that in after the release of 3.4, but there's no firm date as some work on our part and discussion amongst r-core remains before it can happen. So in the future, I hope you'll be able to do this in ways that R sees as actual atomic vectors. They do have to be define in C-code currently, though. ~G On Sun, Mar 5, 2017 at 5:09 PM, <[hidden email]> wrote: > I can't comment for Da, but one example where the ability to make 'if' > generic would have been desirable: > > A couple of years ago I wrote S3 classes and methods for 1-byte integers > and logicals stored as raw vectors, in order to handle massive amounts of > genetic data (by the standards of the day). Everything worked pretty > nicely, ie I could "methodize" just about everything I needed--- except > if-statements, which would fail to respect eg my definitions of NA. [ The > precise details elude me, but if() was untrustworthy. ] To use 'if()', I > had to remember to "typecast", which was prone to "user error". > > Whether this kind of thing is worth the "risk", is another matter. > > cheers > Mark > > Mark Bravington > CSIRO Marine Lab > Hobart > Australia > > ________________________________________ > From: R-devel [[hidden email]] on behalf of Gabriel Becker > [[hidden email]] > Sent: 06 March 2017 11:43 > To: Da Zheng > Cc: [hidden email] > Subject: Re: [Rd] can we override "if" in R? > > Da, > > I've been following this thread and I'm still confused as to exactly what > you want/why you want it. > > I'm probably just missing some context here, but, If() doesn't operate on > matrices, generally. Can you give an example of the type of code you want > to have continue to run that requires if operation *directly* on one of > your matrix objects, as opposed, say, to a value pulled out from it, or the > dot-product of two vectors in your system, both of which would be values > (scalars) not matrices. > > Now ifelse(), is of course, a different beast altogether, and would need to > be overloaded within your system, I imagine. > > Best, > ~G > > On Sun, Mar 5, 2017 at 12:52 PM, Da Zheng <[hidden email]> wrote: > > > On Sun, Mar 5, 2017 at 2:50 PM, Michael Lawrence > > <[hidden email]> wrote: > > > > > > > > > On Sat, Mar 4, 2017 at 12:36 PM, Da Zheng <[hidden email]> > wrote: > > >> > > >> In my case, I create a new type of matrices and override matrix > > >> operations in R for these matrices. > > >> My goal is to make the system as transparent as possible, which means > > >> my system should execute the existing R code without modification. > > >> The problem is that when data is in my own vectors or matrices, "if" > > >> or "while" can't access their values unless we explicitly convert them > > >> into R objects. But this means users need to modify the existing code. > > >> So I hope I can override "if", "while", etc to access data in my own > > >> vectors and matrices directly. > > >> Does this sound reasonable? > > >> > > > > > > Would you really need the alternate representation for scalar logicals? > > > > > > I can see a case in the deferred evaluation context, although it would > be > > > problematic wrt side effects unless the deferral is complete. > > This is exactly why I want to use my own matrix objects and redefine > > "if" for the matrices. In my framework, all matrices are read-only, so > > there isn't side effect. > > > > Best, > > Da > > > > > > > > > > > >> > > >> Best, > > >> Da > > >> > > >> On Sat, Mar 4, 2017 at 3:22 PM, Michael Lawrence > > >> <[hidden email]> wrote: > > >> > I'm curious as to precisely why someone would want to do this. > > >> > > > >> > On Sat, Mar 4, 2017 at 11:49 AM, Da Zheng <[hidden email]> > > wrote: > > >> >> > > >> >> I'm just curious. Why making "if" generic is even more dangerous? > > >> >> > > >> >> Best, > > >> >> Da > > >> >> > > >> >> On Sat, Mar 4, 2017 at 1:22 PM, Gábor Csárdi < > [hidden email] > > > > > >> >> wrote: > > >> >> > `!` is a generic, `if` is not. You can define an `if` that is > > >> >> > generic, > > >> >> > but this might be even more dangerous.... > > >> >> > > > >> >> > ❯ `if` <- function(a, b, c) UseMethod("if") > > >> >> > ❯ `if.default` <- function(a,b,c) base::`if`(a, b, c) > > >> >> > ❯ `if.foo` <- function(a, b, c) FALSE > > >> >> > ❯ a <- structure(42, class = "foo") > > >> >> > > > >> >> > ❯ if (a) TRUE else FALSE > > >> >> > [1] FALSE > > >> >> > > > >> >> > ❯ if (1) TRUE else FALSE > > >> >> > [1] TRUE > > >> >> > > > >> >> > Gabor > > >> >> > > > >> >> > On Sat, Mar 4, 2017 at 5:47 PM, Da Zheng <[hidden email]> > > >> >> > wrote: > > >> >> >> Thanks. > > >> >> >> Can I override it for a specific class? > > >> >> >> I can do that for operators such as "!". For example, "!.fm" > works > > >> >> >> for > > >> >> >> objects of the class "fm". > > >> >> >> It seems I can't do the same for "if". > > >> >> >> > > >> >> >> Best, > > >> >> >> Da > > >> >> >> > > >> >> >> On Sat, Mar 4, 2017 at 12:41 PM, Gábor Csárdi > > >> >> >> <[hidden email]> > > >> >> >> wrote: > > >> >> >>> You can. Perhaps needless to say, be careful with this. > > >> >> >>> > > >> >> >>> ❯ `if` <- function(...) FALSE > > >> >> >>> ❯ if (TRUE) TRUE else FALSE > > >> >> >>> [1] FALSE > > >> >> >>> > > >> >> >>> G. > > >> >> >>> > > >> >> >>> On Sat, Mar 4, 2017 at 5:36 PM, Da Zheng < > [hidden email]> > > >> >> >>> wrote: > > >> >> >>>> Hello, > > >> >> >>>> > > >> >> >>>> I heard we can override almost everything in R. Is it possible > > to > > >> >> >>>> override "if" keyword in R to evaluate my own object instead > of > > a > > >> >> >>>> logical value? > > >> >> >>>> > > >> >> >>>> Thanks, > > >> >> >>>> Da > > >> >> >>>> > > >> >> >>>> ______________________________________________ > > >> >> >>>> [hidden email] mailing list > > >> >> >>>> https://stat.ethz.ch/mailman/listinfo/r-devel > > >> >> > > >> >> ______________________________________________ > > >> >> [hidden email] mailing list > > >> >> https://stat.ethz.ch/mailman/listinfo/r-devel > > >> > > > >> > > > > > > > > > > > ______________________________________________ > > [hidden email] mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > > > -- > Gabriel Becker, PhD > Associate Scientist (Bioinformatics) > Genentech Research > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- Gabriel Becker, PhD Associate Scientist (Bioinformatics) Genentech Research [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
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