Henrik Bengtsson
2016-Oct-19 17:25 UTC
[Rd] How to assign NULL value to pairlist element while keeping it a pairlist?
On Sat, Oct 15, 2016 at 2:00 AM, Martin Maechler <maechler at stat.math.ethz.ch> wrote:>>>>>> Michael Lawrence <lawrence.michael at gene.com> >>>>>> on Wed, 12 Oct 2016 15:21:13 -0700 writes: > > > Thanks, this was what I expected. There is a desire to > > eliminate the usage of pairlist from user code, which > > suggests the alternative of allowing for function > > arguments to be stored in lists. That's a much deeper > > change though. > > and I hope we would not go there just for the purpose of > eliminating pairlists from user code, would we ? > > As nobody else has mentioned it, I'd really like to mention the > two (actually 3) functions important for dealing with function > argument lists much more transparently than the > as.list(<function>) things below: > > formals(<f>) > formals(<f>) <- <arglist> # and > alist() > > for creating / modifying function argument lists (which are > pairlists, but the user does not need to know really). > Or did you imply, Henrik, that would you want is not achievable > with these?Martin, thanks for bringing these options up. Just to make sure no one misreads these comments - I'm not operating on as.list(expr) - it was just used to show the content of the expression. In my case, I'm operating / modifying expressions and not functions per se, e.g. expr <- quote(function(x = 1) x) It's not clear to me how I would go about to modify this to be the equivalent of: expr <- quote(function(x = NULL) x) without having to: f <- eval(expr) formals(f) <- list(x=NULL) expr <- bquote(.(f)) /Henrik> > Martin > > > On Wed, Oct 12, 2016 at 12:31 PM, Henrik Bengtsson > > <henrik.bengtsson at gmail.com> wrote: > >> Michael, thanks for this info. > >> > >> I've stumbled upon this in a case where I walk an R expression (the > >> AST) and (optionally) modifies it (part of the globals package). In R > >> expressions, a function definition uses a pairlist to represent the > >> arguments. For example, > >> > >>> expr <- quote(function(x = 1) x) > >>> str(as.list(expr)) > >> List of 4 > >> $ : symbol function > >> $ :Dotted pair list of 1 > >> ..$ x: num 1 > >> $ : symbol x > >> $ :Class 'srcref' atomic [1:8] 1 15 1 29 15 29 1 1 > >> .. ..- attr(*, "srcfile")=Classes 'srcfilecopy', 'srcfile' > >> <environment: 0x13918b8> > >> > >> Here the 2nd element is a pairlist: > >> > >>> str(expr[[2]]) > >> Dotted pair list of 1 > >> $ x: num 1 > >>> typeof(expr[[2]]) > >> [1] "pairlist" > >> > >> Now say that I want to update the default value of argument 'x', which > >> is currently 1, to NULL. Then I do: > >> > >>> expr[[2]][1] <- list(x = NULL) > >> > >> At this step, I end up with an expression 'expr' where the arguments > >> are no longer represented by a pairlist: > >> > >>> str(expr[[2]]) > >> List of 1 > >> $ x: NULL > >>> typeof(expr[[2]]) > >> [1] "list" > >> > >> More importantly, at this point 'expr' no longer holds a valid R expression: > >> > >>> expr > >> Error: badly formed function expression > >> > >> The solution is to make sure we have a pairlist: > >> > >>> expr[[2]] <- as.pairlist(expr[[2]]) > >>> expr > >> function(x = NULL) x > >> > >> > >> I agree it would be nice to fix this for consistency, but if you bump > >> into major issues, at least I can live with having to use an explicit > >> as.pairlist(). > >> > >> Thanks > >> > >> Henrik > >> > >> On Wed, Oct 12, 2016 at 10:53 AM, Michael Lawrence > >> <lawrence.michael at gene.com> wrote: > >>> Hi Henrik, > >>> > >>> It would help to understand your use case for pairlists. > >>> > >>> Thanks, > >>> Michael > >>> > >>> On Wed, Oct 12, 2016 at 9:40 AM, Michael Lawrence <michafla at gene.com> wrote: > >>>> The coercion is probably the most viable workaround for now, as it's > >>>> consistent with what happens internally for calls. All pairlists/calls > >>>> are converted to list for subassignment, but only calls are converted > >>>> back. My guess is that the intent was for users to move from using a > >>>> pairlist to the "new" (almost 20 years ago) list. In my opinion, > >>>> consistency trumps "convenience" in this case. If others agree, I'll > >>>> change it to also coerce back to pairlist. > >>>> > >>>> Michael > >>>> > >>>> On Wed, Oct 12, 2016 at 9:20 AM, Henrik Bengtsson > >>>> <henrik.bengtsson at gmail.com> wrote: > >>>>> Hi, I seem to not be able to assign NULL to an element of a pairlist > >>>>> without causing it to be coerced to a plain list. For example: > >>>>> >>>>>> x <- pairlist(1, 2) >>>>>> class(x) > >>>>> [1] "pairlist" > >>>>> >>>>>> x[1] <- list(NULL) >>>>>> class(x) > >>>>> [1] "list" > >>>>> > >>>>> This actually true for all [()<- assignments regardless of list value, e.g. > >>>>> >>>>>> x <- pairlist(1, 2) >>>>>> x[1] <- list(0) > >>>>> [1] "list" > >>>>> > >>>>> I also tried assigning a pairlist(), but still the same problem: > >>>>> >>>>>> x <- pairlist(1, 2) >>>>>> x[1] <- pairlist(0) > >>>>> [1] "list" > >>>>> > >>>>> The only workaround I'm aware of is to: > >>>>> > >>>>> x <- as.pairlist(x) > >>>>> > >>>>> at the end. Any other suggestions? > >>>>> > >>>>> Thanks, > >>>>> > >>>>> Henrik > >>>>> > >>>>> ______________________________________________ > >>>>> R-devel at r-project.org mailing list > >>>>> https://stat.ethz.ch/mailman/listinfo/r-devel > > > ______________________________________________ > > R-devel at r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel
luke-tierney at uiowa.edu
2016-Oct-19 18:47 UTC
[Rd] How to assign NULL value to pairlist element while keeping it a pairlist?
On Wed, 19 Oct 2016, Henrik Bengtsson wrote:> On Sat, Oct 15, 2016 at 2:00 AM, Martin Maechler > <maechler at stat.math.ethz.ch> wrote: >>>>>>> Michael Lawrence <lawrence.michael at gene.com> >>>>>>> on Wed, 12 Oct 2016 15:21:13 -0700 writes: >> >> > Thanks, this was what I expected. There is a desire to >> > eliminate the usage of pairlist from user code, which >> > suggests the alternative of allowing for function >> > arguments to be stored in lists. That's a much deeper >> > change though. >> >> and I hope we would not go there just for the purpose of >> eliminating pairlists from user code, would we ? >> >> As nobody else has mentioned it, I'd really like to mention the >> two (actually 3) functions important for dealing with function >> argument lists much more transparently than the >> as.list(<function>) things below: >> >> formals(<f>) >> formals(<f>) <- <arglist> # and >> alist() >> >> for creating / modifying function argument lists (which are >> pairlists, but the user does not need to know really). >> Or did you imply, Henrik, that would you want is not achievable >> with these? > > Martin, thanks for bringing these options up. Just to make sure no > one misreads these comments - I'm not operating on as.list(expr) - it > was just used to show the content of the expression. In my case, > I'm operating / modifying expressions and not functions per se, e.g. > > expr <- quote(function(x = 1) x) > > It's not clear to me how I would go about to modify this to be the > equivalent of: > > expr <- quote(function(x = NULL) x) > > without having to: > > f <- eval(expr) > formals(f) <- list(x=NULL) > expr <- bquote(.(f))You don't need to go through the eval\bquote if you use expr <- quote(function(x = 1) x) alist <- expr[[2]] alist[1] <- list(NULL) expr[[2]] <- as.pairlist(alist) Best, luke> > /Henrik > >> >> Martin >> >> > On Wed, Oct 12, 2016 at 12:31 PM, Henrik Bengtsson >> > <henrik.bengtsson at gmail.com> wrote: >> >> Michael, thanks for this info. >> >> >> >> I've stumbled upon this in a case where I walk an R expression (the >> >> AST) and (optionally) modifies it (part of the globals package). In R >> >> expressions, a function definition uses a pairlist to represent the >> >> arguments. For example, >> >> >> >>> expr <- quote(function(x = 1) x) >> >>> str(as.list(expr)) >> >> List of 4 >> >> $ : symbol function >> >> $ :Dotted pair list of 1 >> >> ..$ x: num 1 >> >> $ : symbol x >> >> $ :Class 'srcref' atomic [1:8] 1 15 1 29 15 29 1 1 >> >> .. ..- attr(*, "srcfile")=Classes 'srcfilecopy', 'srcfile' >> >> <environment: 0x13918b8> >> >> >> >> Here the 2nd element is a pairlist: >> >> >> >>> str(expr[[2]]) >> >> Dotted pair list of 1 >> >> $ x: num 1 >> >>> typeof(expr[[2]]) >> >> [1] "pairlist" >> >> >> >> Now say that I want to update the default value of argument 'x', which >> >> is currently 1, to NULL. Then I do: >> >> >> >>> expr[[2]][1] <- list(x = NULL) >> >> >> >> At this step, I end up with an expression 'expr' where the arguments >> >> are no longer represented by a pairlist: >> >> >> >>> str(expr[[2]]) >> >> List of 1 >> >> $ x: NULL >> >>> typeof(expr[[2]]) >> >> [1] "list" >> >> >> >> More importantly, at this point 'expr' no longer holds a valid R expression: >> >> >> >>> expr >> >> Error: badly formed function expression >> >> >> >> The solution is to make sure we have a pairlist: >> >> >> >>> expr[[2]] <- as.pairlist(expr[[2]]) >> >>> expr >> >> function(x = NULL) x >> >> >> >> >> >> I agree it would be nice to fix this for consistency, but if you bump >> >> into major issues, at least I can live with having to use an explicit >> >> as.pairlist(). >> >> >> >> Thanks >> >> >> >> Henrik >> >> >> >> On Wed, Oct 12, 2016 at 10:53 AM, Michael Lawrence >> >> <lawrence.michael at gene.com> wrote: >> >>> Hi Henrik, >> >>> >> >>> It would help to understand your use case for pairlists. >> >>> >> >>> Thanks, >> >>> Michael >> >>> >> >>> On Wed, Oct 12, 2016 at 9:40 AM, Michael Lawrence <michafla at gene.com> wrote: >> >>>> The coercion is probably the most viable workaround for now, as it's >> >>>> consistent with what happens internally for calls. All pairlists/calls >> >>>> are converted to list for subassignment, but only calls are converted >> >>>> back. My guess is that the intent was for users to move from using a >> >>>> pairlist to the "new" (almost 20 years ago) list. In my opinion, >> >>>> consistency trumps "convenience" in this case. If others agree, I'll >> >>>> change it to also coerce back to pairlist. >> >>>> >> >>>> Michael >> >>>> >> >>>> On Wed, Oct 12, 2016 at 9:20 AM, Henrik Bengtsson >> >>>> <henrik.bengtsson at gmail.com> wrote: >> >>>>> Hi, I seem to not be able to assign NULL to an element of a pairlist >> >>>>> without causing it to be coerced to a plain list. For example: >> >>>>> >>>>>>> x <- pairlist(1, 2) >>>>>>> class(x) >> >>>>> [1] "pairlist" >> >>>>> >>>>>>> x[1] <- list(NULL) >>>>>>> class(x) >> >>>>> [1] "list" >> >>>>> >> >>>>> This actually true for all [()<- assignments regardless of list value, e.g. >> >>>>> >>>>>>> x <- pairlist(1, 2) >>>>>>> x[1] <- list(0) >> >>>>> [1] "list" >> >>>>> >> >>>>> I also tried assigning a pairlist(), but still the same problem: >> >>>>> >>>>>>> x <- pairlist(1, 2) >>>>>>> x[1] <- pairlist(0) >> >>>>> [1] "list" >> >>>>> >> >>>>> The only workaround I'm aware of is to: >> >>>>> >> >>>>> x <- as.pairlist(x) >> >>>>> >> >>>>> at the end. Any other suggestions? >> >>>>> >> >>>>> Thanks, >> >>>>> >> >>>>> Henrik >> >>>>> >> >>>>> ______________________________________________ >> >>>>> R-devel at r-project.org mailing list >> >>>>> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> > ______________________________________________ >> > R-devel at r-project.org mailing list >> > https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >-- Luke Tierney Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics and Fax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: luke-tierney at uiowa.edu Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
Henrik Bengtsson
2016-Oct-19 20:25 UTC
[Rd] How to assign NULL value to pairlist element while keeping it a pairlist?
Thanks Luke. Yes, this is what I wrote as a workaround in my original post (and my first follow up): expr[[2]][1] <- list(x = NULL) expr[[2]] <- as.pairlist(expr[[2]]) but your alist <- expr[[2]] alist[1] <- list(NULL) expr[[2]] <- as.pairlist(alist) makes it a bit more clear what the issue is; a pairlist 'x' (here expr[[2]] and expr) gets coerced to a plain list if one try to do a `[<-()` assignment. It would be nice / useful / less surprising / more consistent(?) if it would remain a pairlist also in those cases. /Henrik On Wed, Oct 19, 2016 at 11:47 AM, <luke-tierney at uiowa.edu> wrote:> On Wed, 19 Oct 2016, Henrik Bengtsson wrote: > >> On Sat, Oct 15, 2016 at 2:00 AM, Martin Maechler >> <maechler at stat.math.ethz.ch> wrote: >>>>>>>> >>>>>>>> Michael Lawrence <lawrence.michael at gene.com> >>>>>>>> on Wed, 12 Oct 2016 15:21:13 -0700 writes: >>> >>> >>> > Thanks, this was what I expected. There is a desire to >>> > eliminate the usage of pairlist from user code, which >>> > suggests the alternative of allowing for function >>> > arguments to be stored in lists. That's a much deeper >>> > change though. >>> >>> and I hope we would not go there just for the purpose of >>> eliminating pairlists from user code, would we ? >>> >>> As nobody else has mentioned it, I'd really like to mention the >>> two (actually 3) functions important for dealing with function >>> argument lists much more transparently than the >>> as.list(<function>) things below: >>> >>> formals(<f>) >>> formals(<f>) <- <arglist> # and >>> alist() >>> >>> for creating / modifying function argument lists (which are >>> pairlists, but the user does not need to know really). >>> Or did you imply, Henrik, that would you want is not achievable >>> with these? >> >> >> Martin, thanks for bringing these options up. Just to make sure no >> one misreads these comments - I'm not operating on as.list(expr) - it >> was just used to show the content of the expression. In my case, >> I'm operating / modifying expressions and not functions per se, e.g. >> >> expr <- quote(function(x = 1) x) >> >> It's not clear to me how I would go about to modify this to be the >> equivalent of: >> >> expr <- quote(function(x = NULL) x) >> >> without having to: >> >> f <- eval(expr) >> formals(f) <- list(x=NULL) >> expr <- bquote(.(f)) > > > You don't need to go through the eval\bquote if you use > > expr <- quote(function(x = 1) x) > alist <- expr[[2]] > alist[1] <- list(NULL) > expr[[2]] <- as.pairlist(alist) > > Best, > > luke > > >> >> /Henrik >> >>> >>> Martin >>> >>> > On Wed, Oct 12, 2016 at 12:31 PM, Henrik Bengtsson >>> > <henrik.bengtsson at gmail.com> wrote: >>> >> Michael, thanks for this info. >>> >> >>> >> I've stumbled upon this in a case where I walk an R expression (the >>> >> AST) and (optionally) modifies it (part of the globals package). >>> In R >>> >> expressions, a function definition uses a pairlist to represent the >>> >> arguments. For example, >>> >> >>> >>> expr <- quote(function(x = 1) x) >>> >>> str(as.list(expr)) >>> >> List of 4 >>> >> $ : symbol function >>> >> $ :Dotted pair list of 1 >>> >> ..$ x: num 1 >>> >> $ : symbol x >>> >> $ :Class 'srcref' atomic [1:8] 1 15 1 29 15 29 1 1 >>> >> .. ..- attr(*, "srcfile")=Classes 'srcfilecopy', 'srcfile' >>> >> <environment: 0x13918b8> >>> >> >>> >> Here the 2nd element is a pairlist: >>> >> >>> >>> str(expr[[2]]) >>> >> Dotted pair list of 1 >>> >> $ x: num 1 >>> >>> typeof(expr[[2]]) >>> >> [1] "pairlist" >>> >> >>> >> Now say that I want to update the default value of argument 'x', >>> which >>> >> is currently 1, to NULL. Then I do: >>> >> >>> >>> expr[[2]][1] <- list(x = NULL) >>> >> >>> >> At this step, I end up with an expression 'expr' where the >>> arguments >>> >> are no longer represented by a pairlist: >>> >> >>> >>> str(expr[[2]]) >>> >> List of 1 >>> >> $ x: NULL >>> >>> typeof(expr[[2]]) >>> >> [1] "list" >>> >> >>> >> More importantly, at this point 'expr' no longer holds a valid R >>> expression: >>> >> >>> >>> expr >>> >> Error: badly formed function expression >>> >> >>> >> The solution is to make sure we have a pairlist: >>> >> >>> >>> expr[[2]] <- as.pairlist(expr[[2]]) >>> >>> expr >>> >> function(x = NULL) x >>> >> >>> >> >>> >> I agree it would be nice to fix this for consistency, but if you >>> bump >>> >> into major issues, at least I can live with having to use an >>> explicit >>> >> as.pairlist(). >>> >> >>> >> Thanks >>> >> >>> >> Henrik >>> >> >>> >> On Wed, Oct 12, 2016 at 10:53 AM, Michael Lawrence >>> >> <lawrence.michael at gene.com> wrote: >>> >>> Hi Henrik, >>> >>> >>> >>> It would help to understand your use case for pairlists. >>> >>> >>> >>> Thanks, >>> >>> Michael >>> >>> >>> >>> On Wed, Oct 12, 2016 at 9:40 AM, Michael Lawrence >>> <michafla at gene.com> wrote: >>> >>>> The coercion is probably the most viable workaround for now, as >>> it's >>> >>>> consistent with what happens internally for calls. All >>> pairlists/calls >>> >>>> are converted to list for subassignment, but only calls are >>> converted >>> >>>> back. My guess is that the intent was for users to move from >>> using a >>> >>>> pairlist to the "new" (almost 20 years ago) list. In my opinion, >>> >>>> consistency trumps "convenience" in this case. If others agree, >>> I'll >>> >>>> change it to also coerce back to pairlist. >>> >>>> >>> >>>> Michael >>> >>>> >>> >>>> On Wed, Oct 12, 2016 at 9:20 AM, Henrik Bengtsson >>> >>>> <henrik.bengtsson at gmail.com> wrote: >>> >>>>> Hi, I seem to not be able to assign NULL to an element of a >>> pairlist >>> >>>>> without causing it to be coerced to a plain list. For example: >>> >>>>> >>>>>>>> >>>>>>>> x <- pairlist(1, 2) >>>>>>>> class(x) >>> >>> >>>>> [1] "pairlist" >>> >>>>> >>>>>>>> >>>>>>>> x[1] <- list(NULL) >>>>>>>> class(x) >>> >>> >>>>> [1] "list" >>> >>>>> >>> >>>>> This actually true for all [()<- assignments regardless of list >>> value, e.g. >>> >>>>> >>>>>>>> >>>>>>>> x <- pairlist(1, 2) >>>>>>>> x[1] <- list(0) >>> >>> >>>>> [1] "list" >>> >>>>> >>> >>>>> I also tried assigning a pairlist(), but still the same problem: >>> >>>>> >>>>>>>> >>>>>>>> x <- pairlist(1, 2) >>>>>>>> x[1] <- pairlist(0) >>> >>> >>>>> [1] "list" >>> >>>>> >>> >>>>> The only workaround I'm aware of is to: >>> >>>>> >>> >>>>> x <- as.pairlist(x) >>> >>>>> >>> >>>>> at the end. Any other suggestions? >>> >>>>> >>> >>>>> Thanks, >>> >>>>> >>> >>>>> Henrik >>> >>>>> >>> >>>>> ______________________________________________ >>> >>>>> R-devel at r-project.org mailing list >>> >>>>> https://stat.ethz.ch/mailman/listinfo/r-devel >>> >>> > ______________________________________________ >>> > R-devel at r-project.org mailing list >>> > https://stat.ethz.ch/mailman/listinfo/r-devel >> >> >> ______________________________________________ >> R-devel at r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > > -- > Luke Tierney > Ralph E. Wareham Professor of Mathematical Sciences > University of Iowa Phone: 319-335-3386 > Department of Statistics and Fax: 319-335-3017 > Actuarial Science > 241 Schaeffer Hall email: luke-tierney at uiowa.edu > Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
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