Re: [R-pkg-devel] R feature suggestion: Duplicated function arguments check
Thanks for your replies, I only just noticed them as I had daily-digest =
true and someone seems to have removed my e-mail address when replying to
the list. Never mind, I have now switched my daily-digest to false.
Yes - The issue is that "myfun(A = 1, B = 2, B = 4)" in the example below
is ambiguous and only the end-user knows whether B should be 2 or 4.
Either way, I will just implement my own solution. Just wanted to report
that I ran into this situation and maybe others too.
Best, Vincent
On Mon, 8 Nov 2021 at 17:24, Vincent van Hees
wrote:
> Thanks Duncan, I have tried to make a minimalistic example:
>
> myfun = function(...) {
> input = list(...)
> mysum = function(A = c(), B= c()) {
> return(A+B)
> }
> if ("A" %in% names(input) & "B" %in% names(input)) {
> print(mysum(A = input$A, B = input$B))
> }
> }
>
> # test:
> > myfun(A = 1, B = 2, B = 4)
> [1] 3
>
> # So, the second B is ignored.
>
>
>
> On Mon, 8 Nov 2021 at 17:03, Duncan Murdoch
> wrote:
>
>> On 08/11/2021 10:29 a.m., Vincent van Hees wrote:
>> > Not sure if this is the best place to post this message, as it is more
>> of a
>> > suggestion than a question.
>> >
>> > When an R function accepts more than a handful of arguments there is the
>> > risk that users accidentally provide arguments twice, e.g myfun(A=1,
>> B=2,
>> > C=4, D=5, A=7), and if those two values are not the same it can have
>> > frustrating side-effects. To catch this I am planning to add a check for
>> > duplicated arguments, as shown below, in one of my own functions. I am
>> now
>> > wondering whether this would be a useful feature for R itself to
>> operate in
>> > the background when running any R function that has more than a certain
>> > number of input arguments.
>> >
>> > Cheers, Vincent
>> >
>> > myfun = function(...) {
>> >#check input arguments for duplicate assignments
>> >input = list(...)
>> >if (length(input) > 0) {
>> > argNames = names(input)
>> > dupArgNames = duplicated(argNames)
>> > if (any(dupArgNames)) {
>> >for (dupi in unique(argNames[dupArgNames])) {
>> > dupArgValues = input[which(argNames %in% dupi)]
>> > if (all(dupArgValues == dupArgValues[[1]])) { # double
>> arguments,
>> > but no confusion about what value should be
>> >warning(paste0("\nArgument ", dupi, " has been provided more
>> than
>> > once in the same call, which is ambiguous. Please fix."))
>> > } else { # double arguments, and confusion about what value
>> should
>> > be,
>> >stop(paste0("\nArgument ", dupi, " has been provided more
>> than
>> > once in the same call, which is ambiguous. Please fix."))
>> > }
>> >}
>> > }
>> >}
>> ># rest of code...
>> > }
>> >
>>
>> Could you give an example where this is needed? If a named argument is
>> duplicated, R will catch that and give an error message:
>>
>>> f(a=1, b=2, a=3)
>>Error in f(a = 1, b = 2, a = 3) :
>> formal argument "a" matched by multiple actual arguments
>>
>> So this can only happen when it is an argument in the ... list that is
>> duplicated. But usually those are passed to some other function, so
>> something like
>>
>>g <- function(...) f(...)
>>
>> would also catch the duplication in g(a=1, b=2, a=3):
>>
>>> g(a=1, b=2, a=3)
>>Error in f(...) :
>> formal argument "a" matched by multiple actual arguments
>>
>> The only case where I can see this getting by is where you are never
>> using those arguments to match any formal argument, e.g.
>>
>>list(a=1, b=2, a=3)
>>
>> Maybe this should have been made illegal when R was created, but I think
>> it's too late to outlaw now: I'm sure there are lots of people making
>> use of this.
>>
>> Or am I missing something?
>>
>> Duncan Murdoch
>>
>
[[alternative HTML version deleted]]
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
Re: [R-pkg-devel] R feature suggestion: Duplicated function arguments check
I think this is similar in nature (though not detail) to an issue raised
on StackOverflow where the OP used "x" in dot args and it clashed with the
"x" in a numDeriv call in my optimx package. I've got a very early fix (I
think), though moderators on StackOverflow were unpleasant enough to
delete my request for the OP to contact me so I could get more
information to make improvements. Sigh. Developers need conversations
with users to improve their code.
Re: argument duplication -- In my view, the first goal should be to inform
the user of the clash. Doing anything further without providing information
is likely a very bad idea, though discussion of possibilities of action after
notification is certainly worthwhile.
Best, JN
On 2021-11-08 11:53 a.m., Duncan Murdoch wrote:
On 08/11/2021 11:48 a.m., Avi Gross via R-package-devel wrote:
Vincent,
But is the second being ignored the right result?
In many programming situations, subsequent assignments replace earlier ones.
And consider the way R allows something like this:
func(a=2, b=3, a=4, c=a*b)
Is it clear how to initialize the default for c as it depends on one value
of "a" or the other?
That c=a*b only works with non-standard tidyverse evaluation. It causes other problems, e.g. the inability to pass ...
properly (see https://github.com/tidyverse/glue/issues/231 for an example).
Duncan Murdoch
Of course, you could just make multiple settings an error rather than
choosing an arbitrary fix.
R lists are more like a BAG data structure than a SET.
-Original Message-
From: R-package-devel On Behalf Of
Vincent van Hees
Sent: Monday, November 8, 2021 11:25 AM
To: Duncan Murdoch
Cc: r-package-devel@r-project.org
Subject: Re: [R-pkg-devel] R feature suggestion: Duplicated function
arguments check
Thanks Duncan, I have tried to make a minimalistic example:
myfun = function(...) {
input = list(...)
mysum = function(A = c(), B= c()) {
return(A+B)
}
if ("A" %in% names(input) & "B" %in% names(input)) {
print(mysum(A = input$A, B = input$B))
}
}
# test:
myfun(A = 1, B = 2, B = 4)
[1] 3
# So, the second B is ignored.
On Mon, 8 Nov 2021 at 17:03, Duncan Murdoch
wrote:
On 08/11/2021 10:29 a.m., Vincent van Hees wrote:
Not sure if this is the best place to post this message, as it is
more
of a
suggestion than a question.
When an R function accepts more than a handful of arguments there is
the risk that users accidentally provide arguments twice, e.g
myfun(A=1, B=2, C=4, D=5, A=7), and if those two values are not the
same it can have frustrating side-effects. To catch this I am
planning to add a check for duplicated arguments, as shown below, in
one of my own functions. I am
now
wondering whether this would be a useful feature for R itself to
operate
in
the background when running any R function that has more than a
certain number of input arguments.
Cheers, Vincent
myfun = function(...) {
#check input arguments for duplicate assignments
input = list(...)
if (length(input) > 0) {
argNames = names(input)
dupArgNames = duplicated(argNames)
if (any(dupArgNames)) {
for (dupi in unique(argNames[dupArgNames])) {
dupArgValues = input[which(argNames %in% dupi)]
if (all(dupArgValues == dupArgValues[[1]])) { # double
arguments,
but no confusion about what value should be
warning(paste0("\nArgument ", dupi, " has been provided
more
than
once in the same call, which is ambiguous. Please fix."))
} else { # double arguments, and confusion about what value
should
be,
stop(paste0("\nArgument ", dupi, " has been provided more
than once in the same call, which is ambiguous. Please fix."))
}
}
}
}
# rest of code...
}
Could you give an example where this is needed? If a named argument
is duplicated, R will catch that and give an error message:
> f(a=1, b=2, a=3)
Error in f(a = 1, b = 2, a = 3) :
formal argument "a" matched by multiple actual arguments
So this can only happen when it is an argument in the ... list that is
duplicated. But usually those are passed to some other function, so
something like
g <- function(...) f(...)
would also catch the duplication in g(a=1, b=2, a=3):
> g(a=1, b=2, a=3)
Error in f(...) :
formal argument "a" matched by multiple actual arguments
The only case where I can see this getting by is where you are never
using those arguments to match any formal argument, e.g.
list(a=1, b=2, a=3)
Maybe this should have been made illegal when R was created, but I
think it's too late to outlaw now: I'm sure there are lots of people
making use of this.
Or am I missing something?
Duncan Murdoch
[[alternative HTML version deleted]]
_
Re: [R-pkg-devel] R feature suggestion: Duplicated function arguments check
On 08/11/2021 11:48 a.m., Avi Gross via R-package-devel wrote:
Vincent,
But is the second being ignored the right result?
In many programming situations, subsequent assignments replace earlier ones.
And consider the way R allows something like this:
func(a=2, b=3, a=4, c=a*b)
Is it clear how to initialize the default for c as it depends on one value
of "a" or the other?
That c=a*b only works with non-standard tidyverse evaluation. It causes
other problems, e.g. the inability to pass ... properly (see
https://github.com/tidyverse/glue/issues/231 for an example).
Duncan Murdoch
Of course, you could just make multiple settings an error rather than
choosing an arbitrary fix.
R lists are more like a BAG data structure than a SET.
-Original Message-
From: R-package-devel On Behalf Of
Vincent van Hees
Sent: Monday, November 8, 2021 11:25 AM
To: Duncan Murdoch
Cc: r-package-devel@r-project.org
Subject: Re: [R-pkg-devel] R feature suggestion: Duplicated function
arguments check
Thanks Duncan, I have tried to make a minimalistic example:
myfun = function(...) {
input = list(...)
mysum = function(A = c(), B= c()) {
return(A+B)
}
if ("A" %in% names(input) & "B" %in% names(input)) {
print(mysum(A = input$A, B = input$B))
}
}
# test:
myfun(A = 1, B = 2, B = 4)
[1] 3
# So, the second B is ignored.
On Mon, 8 Nov 2021 at 17:03, Duncan Murdoch
wrote:
On 08/11/2021 10:29 a.m., Vincent van Hees wrote:
Not sure if this is the best place to post this message, as it is
more
of a
suggestion than a question.
When an R function accepts more than a handful of arguments there is
the risk that users accidentally provide arguments twice, e.g
myfun(A=1, B=2, C=4, D=5, A=7), and if those two values are not the
same it can have frustrating side-effects. To catch this I am
planning to add a check for duplicated arguments, as shown below, in
one of my own functions. I am
now
wondering whether this would be a useful feature for R itself to
operate
in
the background when running any R function that has more than a
certain number of input arguments.
Cheers, Vincent
myfun = function(...) {
#check input arguments for duplicate assignments
input = list(...)
if (length(input) > 0) {
argNames = names(input)
dupArgNames = duplicated(argNames)
if (any(dupArgNames)) {
for (dupi in unique(argNames[dupArgNames])) {
dupArgValues = input[which(argNames %in% dupi)]
if (all(dupArgValues == dupArgValues[[1]])) { # double
arguments,
but no confusion about what value should be
warning(paste0("\nArgument ", dupi, " has been provided
more
than
once in the same call, which is ambiguous. Please fix."))
} else { # double arguments, and confusion about what value
should
be,
stop(paste0("\nArgument ", dupi, " has been provided more
than once in the same call, which is ambiguous. Please fix."))
}
}
}
}
# rest of code...
}
Could you give an example where this is needed? If a named argument
is duplicated, R will catch that and give an error message:
> f(a=1, b=2, a=3)
Error in f(a = 1, b = 2, a = 3) :
formal argument "a" matched by multiple actual arguments
So this can only happen when it is an argument in the ... list that is
duplicated. But usually those are passed to some other function, so
something like
g <- function(...) f(...)
would also catch the duplication in g(a=1, b=2, a=3):
> g(a=1, b=2, a=3)
Error in f(...) :
formal argument "a" matched by multiple actual arguments
The only case where I can see this getting by is where you are never
using those arguments to match any formal argument, e.g.
list(a=1, b=2, a=3)
Maybe this should have been made illegal when R was created, but I
think it's too late to outlaw now: I'm sure there are lots of people
making use of this.
Or am I missing something?
Duncan Murdoch
[[alternative HTML version deleted]]
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
Re: [R-pkg-devel] R feature suggestion: Duplicated function arguments check
Vincent,
But is the second being ignored the right result?
In many programming situations, subsequent assignments replace earlier ones.
And consider the way R allows something like this:
func(a=2, b=3, a=4, c=a*b)
Is it clear how to initialize the default for c as it depends on one value
of "a" or the other?
Of course, you could just make multiple settings an error rather than
choosing an arbitrary fix.
R lists are more like a BAG data structure than a SET.
-Original Message-
From: R-package-devel On Behalf Of
Vincent van Hees
Sent: Monday, November 8, 2021 11:25 AM
To: Duncan Murdoch
Cc: r-package-devel@r-project.org
Subject: Re: [R-pkg-devel] R feature suggestion: Duplicated function
arguments check
Thanks Duncan, I have tried to make a minimalistic example:
myfun = function(...) {
input = list(...)
mysum = function(A = c(), B= c()) {
return(A+B)
}
if ("A" %in% names(input) & "B" %in% names(input)) {
print(mysum(A = input$A, B = input$B))
}
}
# test:
> myfun(A = 1, B = 2, B = 4)
[1] 3
# So, the second B is ignored.
On Mon, 8 Nov 2021 at 17:03, Duncan Murdoch
wrote:
> On 08/11/2021 10:29 a.m., Vincent van Hees wrote:
> > Not sure if this is the best place to post this message, as it is
> > more
> of a
> > suggestion than a question.
> >
> > When an R function accepts more than a handful of arguments there is
> > the risk that users accidentally provide arguments twice, e.g
> > myfun(A=1, B=2, C=4, D=5, A=7), and if those two values are not the
> > same it can have frustrating side-effects. To catch this I am
> > planning to add a check for duplicated arguments, as shown below, in
> > one of my own functions. I am
> now
> > wondering whether this would be a useful feature for R itself to
> > operate
> in
> > the background when running any R function that has more than a
> > certain number of input arguments.
> >
> > Cheers, Vincent
> >
> > myfun = function(...) {
> >#check input arguments for duplicate assignments
> >input = list(...)
> >if (length(input) > 0) {
> > argNames = names(input)
> > dupArgNames = duplicated(argNames)
> > if (any(dupArgNames)) {
> >for (dupi in unique(argNames[dupArgNames])) {
> > dupArgValues = input[which(argNames %in% dupi)]
> > if (all(dupArgValues == dupArgValues[[1]])) { # double
> arguments,
> > but no confusion about what value should be
> >warning(paste0("\nArgument ", dupi, " has been provided
> > more
> than
> > once in the same call, which is ambiguous. Please fix."))
> > } else { # double arguments, and confusion about what value
> should
> > be,
> >stop(paste0("\nArgument ", dupi, " has been provided more
> > than once in the same call, which is ambiguous. Please fix."))
> > }
> >}
> > }
> >}
> ># rest of code...
> > }
> >
>
> Could you give an example where this is needed? If a named argument
> is duplicated, R will catch that and give an error message:
>
>> f(a=1, b=2, a=3)
>Error in f(a = 1, b = 2, a = 3) :
> formal argument "a" matched by multiple actual arguments
>
> So this can only happen when it is an argument in the ... list that is
> duplicated. But usually those are passed to some other function, so
> something like
>
>g <- function(...) f(...)
>
> would also catch the duplication in g(a=1, b=2, a=3):
>
>> g(a=1, b=2, a=3)
>Error in f(...) :
> formal argument "a" matched by multiple actual arguments
>
> The only case where I can see this getting by is where you are never
> using those arguments to match any formal argument, e.g.
>
>list(a=1, b=2, a=3)
>
> Maybe this should have been made illegal when R was created, but I
> think it's too late to outlaw now: I'm sure there are lots of people
> making use of this.
>
> Or am I missing something?
>
> Duncan Murdoch
>
[[alternative HTML version deleted]]
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
Re: [R-pkg-devel] R feature suggestion: Duplicated function arguments check
Thanks Duncan, I have tried to make a minimalistic example:
myfun = function(...) {
input = list(...)
mysum = function(A = c(), B= c()) {
return(A+B)
}
if ("A" %in% names(input) & "B" %in% names(input)) {
print(mysum(A = input$A, B = input$B))
}
}
# test:
> myfun(A = 1, B = 2, B = 4)
[1] 3
# So, the second B is ignored.
On Mon, 8 Nov 2021 at 17:03, Duncan Murdoch
wrote:
> On 08/11/2021 10:29 a.m., Vincent van Hees wrote:
> > Not sure if this is the best place to post this message, as it is more
> of a
> > suggestion than a question.
> >
> > When an R function accepts more than a handful of arguments there is the
> > risk that users accidentally provide arguments twice, e.g myfun(A=1, B=2,
> > C=4, D=5, A=7), and if those two values are not the same it can have
> > frustrating side-effects. To catch this I am planning to add a check for
> > duplicated arguments, as shown below, in one of my own functions. I am
> now
> > wondering whether this would be a useful feature for R itself to operate
> in
> > the background when running any R function that has more than a certain
> > number of input arguments.
> >
> > Cheers, Vincent
> >
> > myfun = function(...) {
> >#check input arguments for duplicate assignments
> >input = list(...)
> >if (length(input) > 0) {
> > argNames = names(input)
> > dupArgNames = duplicated(argNames)
> > if (any(dupArgNames)) {
> >for (dupi in unique(argNames[dupArgNames])) {
> > dupArgValues = input[which(argNames %in% dupi)]
> > if (all(dupArgValues == dupArgValues[[1]])) { # double
> arguments,
> > but no confusion about what value should be
> >warning(paste0("\nArgument ", dupi, " has been provided more
> than
> > once in the same call, which is ambiguous. Please fix."))
> > } else { # double arguments, and confusion about what value
> should
> > be,
> >stop(paste0("\nArgument ", dupi, " has been provided more than
> > once in the same call, which is ambiguous. Please fix."))
> > }
> >}
> > }
> >}
> ># rest of code...
> > }
> >
>
> Could you give an example where this is needed? If a named argument is
> duplicated, R will catch that and give an error message:
>
>> f(a=1, b=2, a=3)
>Error in f(a = 1, b = 2, a = 3) :
> formal argument "a" matched by multiple actual arguments
>
> So this can only happen when it is an argument in the ... list that is
> duplicated. But usually those are passed to some other function, so
> something like
>
>g <- function(...) f(...)
>
> would also catch the duplication in g(a=1, b=2, a=3):
>
>> g(a=1, b=2, a=3)
>Error in f(...) :
> formal argument "a" matched by multiple actual arguments
>
> The only case where I can see this getting by is where you are never
> using those arguments to match any formal argument, e.g.
>
>list(a=1, b=2, a=3)
>
> Maybe this should have been made illegal when R was created, but I think
> it's too late to outlaw now: I'm sure there are lots of people making
> use of this.
>
> Or am I missing something?
>
> Duncan Murdoch
>
[[alternative HTML version deleted]]
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
Re: [R-pkg-devel] R feature suggestion: Duplicated function arguments check
Duncan,
This may not be the place to discuss this so I will be brief.
The question is whether it should be some kind of error to call a function
with two named arguments that are the same.
I can think of a perhaps valid use when a function expects to take the first
few arguments for personal use and then uses ... to pass the rest along to
other functions it calls.
so in your case, slightly extended:
f(a=1, b=2, a=3, c=-5)
The function might pass along to another function:
other(arg, ...)
which would be seen as:
other(arg, a=3, c=-5)
There can of course be other ways to get this result but probably not as
simple. And note this can go several layers deep as various functions call
each other and each has a different need and even meaning for a=something.
Avi
-Original Message-
From: R-package-devel On Behalf Of
Duncan Murdoch
Sent: Monday, November 8, 2021 11:04 AM
To: Vincent van Hees ;
r-package-devel@r-project.org
Subject: Re: [R-pkg-devel] R feature suggestion: Duplicated function
arguments check
On 08/11/2021 10:29 a.m., Vincent van Hees wrote:
> Not sure if this is the best place to post this message, as it is more
> of a suggestion than a question.
>
> When an R function accepts more than a handful of arguments there is
> the risk that users accidentally provide arguments twice, e.g
> myfun(A=1, B=2, C=4, D=5, A=7), and if those two values are not the
> same it can have frustrating side-effects. To catch this I am planning
> to add a check for duplicated arguments, as shown below, in one of my
> own functions. I am now wondering whether this would be a useful
> feature for R itself to operate in the background when running any R
> function that has more than a certain number of input arguments.
>
> Cheers, Vincent
>
> myfun = function(...) {
>#check input arguments for duplicate assignments
>input = list(...)
>if (length(input) > 0) {
> argNames = names(input)
> dupArgNames = duplicated(argNames)
> if (any(dupArgNames)) {
>for (dupi in unique(argNames[dupArgNames])) {
> dupArgValues = input[which(argNames %in% dupi)]
> if (all(dupArgValues == dupArgValues[[1]])) { # double
> arguments, but no confusion about what value should be
>warning(paste0("\nArgument ", dupi, " has been provided
> more than once in the same call, which is ambiguous. Please fix."))
> } else { # double arguments, and confusion about what value
> should be,
>stop(paste0("\nArgument ", dupi, " has been provided more
> than once in the same call, which is ambiguous. Please fix."))
> }
>}
> }
>}
># rest of code...
> }
>
Could you give an example where this is needed? If a named argument is
duplicated, R will catch that and give an error message:
> f(a=1, b=2, a=3)
Error in f(a = 1, b = 2, a = 3) :
formal argument "a" matched by multiple actual arguments
So this can only happen when it is an argument in the ... list that is
duplicated. But usually those are passed to some other function, so
something like
g <- function(...) f(...)
would also catch the duplication in g(a=1, b=2, a=3):
> g(a=1, b=2, a=3)
Error in f(...) :
formal argument "a" matched by multiple actual arguments
The only case where I can see this getting by is where you are never using
those arguments to match any formal argument, e.g.
list(a=1, b=2, a=3)
Maybe this should have been made illegal when R was created, but I think
it's too late to outlaw now: I'm sure there are lots of people making use
of this.
Or am I missing something?
Duncan Murdoch
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
Re: [R-pkg-devel] R feature suggestion: Duplicated function arguments check
On 08/11/2021 10:29 a.m., Vincent van Hees wrote:
Not sure if this is the best place to post this message, as it is more of a
suggestion than a question.
When an R function accepts more than a handful of arguments there is the
risk that users accidentally provide arguments twice, e.g myfun(A=1, B=2,
C=4, D=5, A=7), and if those two values are not the same it can have
frustrating side-effects. To catch this I am planning to add a check for
duplicated arguments, as shown below, in one of my own functions. I am now
wondering whether this would be a useful feature for R itself to operate in
the background when running any R function that has more than a certain
number of input arguments.
Cheers, Vincent
myfun = function(...) {
#check input arguments for duplicate assignments
input = list(...)
if (length(input) > 0) {
argNames = names(input)
dupArgNames = duplicated(argNames)
if (any(dupArgNames)) {
for (dupi in unique(argNames[dupArgNames])) {
dupArgValues = input[which(argNames %in% dupi)]
if (all(dupArgValues == dupArgValues[[1]])) { # double arguments,
but no confusion about what value should be
warning(paste0("\nArgument ", dupi, " has been provided more than
once in the same call, which is ambiguous. Please fix."))
} else { # double arguments, and confusion about what value should
be,
stop(paste0("\nArgument ", dupi, " has been provided more than
once in the same call, which is ambiguous. Please fix."))
}
}
}
}
# rest of code...
}
Could you give an example where this is needed? If a named argument is
duplicated, R will catch that and give an error message:
> f(a=1, b=2, a=3)
Error in f(a = 1, b = 2, a = 3) :
formal argument "a" matched by multiple actual arguments
So this can only happen when it is an argument in the ... list that is
duplicated. But usually those are passed to some other function, so
something like
g <- function(...) f(...)
would also catch the duplication in g(a=1, b=2, a=3):
> g(a=1, b=2, a=3)
Error in f(...) :
formal argument "a" matched by multiple actual arguments
The only case where I can see this getting by is where you are never
using those arguments to match any formal argument, e.g.
list(a=1, b=2, a=3)
Maybe this should have been made illegal when R was created, but I think
it's too late to outlaw now: I'm sure there are lots of people making
use of this.
Or am I missing something?
Duncan Murdoch
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
[R-pkg-devel] R feature suggestion: Duplicated function arguments check
Not sure if this is the best place to post this message, as it is more of a
suggestion than a question.
When an R function accepts more than a handful of arguments there is the
risk that users accidentally provide arguments twice, e.g myfun(A=1, B=2,
C=4, D=5, A=7), and if those two values are not the same it can have
frustrating side-effects. To catch this I am planning to add a check for
duplicated arguments, as shown below, in one of my own functions. I am now
wondering whether this would be a useful feature for R itself to operate in
the background when running any R function that has more than a certain
number of input arguments.
Cheers, Vincent
myfun = function(...) {
#check input arguments for duplicate assignments
input = list(...)
if (length(input) > 0) {
argNames = names(input)
dupArgNames = duplicated(argNames)
if (any(dupArgNames)) {
for (dupi in unique(argNames[dupArgNames])) {
dupArgValues = input[which(argNames %in% dupi)]
if (all(dupArgValues == dupArgValues[[1]])) { # double arguments,
but no confusion about what value should be
warning(paste0("\nArgument ", dupi, " has been provided more than
once in the same call, which is ambiguous. Please fix."))
} else { # double arguments, and confusion about what value should
be,
stop(paste0("\nArgument ", dupi, " has been provided more than
once in the same call, which is ambiguous. Please fix."))
}
}
}
}
# rest of code...
}
[[alternative HTML version deleted]]
__
R-package-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-package-devel
