subject:"Re\: \[R\] Strange lazy evaluation of default arguments"

Re: [R] Strange lazy evaluation of default arguments

2017-09-05 Thread Jeff Newmiller

>In the future, I’ll avoid dependencies between parameters.

You don't need to cut off your nose to spite your face... you are the one 
writing the code that breaks the dependency, so you have the option to not 
write your code that way (e.g. by using force() as Rui suggests).
-- 
Sent from my phone. Please excuse my brevity.

On September 2, 2017 10:53:14 AM PDT, Matthias Gondan <matthias-gon...@gmx.de> 
wrote:
>Dear Bill,
>
>All makes perfect sense (including the late evaluation). I actually
>discovered the problem by looking at old code which used your proposed
>solution. Still I find it strange (and, hnestly, I don’t like R’s
>behavior in this respect), and I am wondering why u is not being copied
>to L just before u is assigned a new value. Of course, this would
>require the R interpreter to track all these dependencies in both ways
>incl. more complicated ones in which L might depend on more than just
>u.
>
>In the future, I’ll avoid dependencies between parameters.
>
>Su4 <- function(u=100, l=100, mu=0.53, sigma2=4.3^2) # instead of l=u
>
>And maybe also „in-place“ changes of values…
>
>Best regards,
>
>Matthias
>
>Von: William Dunlap
>Gesendet: Samstag, 2. September 2017 19:41
>An: Rui Barradas
>Cc: Matthias Gondan; r-help@r-project.org
>Betreff: Re: [R] Strange lazy evaluation of default arguments
>
>Another way to avoid the problem is to not redefine variables that are
>arguments.  E.g.,
>
>> Su3 <- function(u=100, l=u, mu=0.53, sigma2=4.3^2, verbose)
>  {
>    if (verbose) {
>      print(c(u, l, mu))
>    }
>    uNormalized <- u/sqrt(sigma2)
>    lNormalized <- l/sqrt(sigma2)
>    muNormalized <- mu/sqrt(sigma2)
>    c(uNormalized, lNormalized, muNormalized)
>  }
>> Su3(verbose=TRUE)
>[1] 100.00 100.00   0.53
>[1] 23.2558140 23.2558140  0.1232558
>> Su3(verbose=FALSE)
>[1] 23.2558140 23.2558140  0.1232558
>
>Not redefining variables at all makes debugging easier, although it may
>waste space.
>
>
>Bill Dunlap
>TIBCO Software
>wdunlap tibco.com
>
>On Sat, Sep 2, 2017 at 10:33 AM, <ruipbarra...@sapo.pt> wrote:
>Hello,
>
>One way of preventing that is to use ?force.
>Just put
>
>   force(l)
>
>right after the commented out print and before you change 'u'.
>
>Hope this helps,
>
>Rui Barradas
>
>
>
>Citando Matthias Gondan <matthias-gon...@gmx.de>:
>
>Dear R developers,
>
>sessionInfo() below
>
>Please have a look at the following two versions of the same function:
>
>1. Intended behavior:
>Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
>+ {
>+   print(c(u, l, mu)) # here, l is set to u’s value
>+   u = u/sqrt(sigma2)
>+   l = l/sqrt(sigma2)
>+   mu = mu/sqrt(sigma2)
>+   print(c(u, l, mu))
>+ }
>
>Su1()
>[1] 100.00 100.00   0.53
>[1] 23.2558140 23.2558140  0.1232558
>
>In the first version, both u and l are correctly divided by 4.3.
>
>2. Strange behavior:
>Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
>+ {
>+   # print(c(u, l, mu))
>+   u = u/sqrt(sigma2)
>+   l = l/sqrt(sigma2) # here, l is set to u’s value
>+   mu = mu/sqrt(sigma2)
>+   print(c(u, l, mu))
>+ }
>
>Su2()
>[1] 23.2558140  5.4083288  0.1232558
>In the second version, the print
>function is commented out, so the variable u is
>copied to l (lowercase L) at a later place, and L is divided twice by
>4.3.
>
>Is this behavior intended? It seems strange that the result depends on
>a debugging message.
>
>Best wishes,
>
>Matthias
>
>sessionInfo()
>R version 3.4.1 (2017-06-30)
>Platform: x86_64-w64-mingw32/x64 (64-bit)
>Running under: Windows >= 8 x64 (build 9200)
>
>Matrix products: default
>
>locale:
>[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252   
>LC_MONETARY=German_Germany.1252
>[4] LC_NUMERIC=C                    LC_TIME=German_Germany.1252
>
>attached base packages:
>[1] stats     graphics  grDevices utils     datasets  methods   base
>
>loaded via a namespace (and not attached):
>[1] compiler_3.4.1 tools_3.4.1
>
>
>        [[alternative HTML version deleted]]
>
>__
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
>
>__
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and p

Re: [R] Strange lazy evaluation of default arguments

2017-09-05 Thread Matthias Gondan

Dear S Ellison,

Thanks for the flowers! Indeed, I was actually considering to use it in my own 
teaching material, as well. With rounded numbers, of course.

Though I am still slightly disturbed about this feature. I thought, now it is 
the time to switch to Python, but that’s even worse, see here:

def add_elem(List=[]):
List.append('elem')
return List

>>> add_elem([2])
[2, 'elem']
>>> add_elem()
['elem']
>>> add_elem()
['elem', 'elem'] <<<<<<<<<<< why on earth does this happen? [it’s documented 
behavior, but still…]

So, I’ll stick with R. Still 25 years or so until retirement, but I’ll survive, 
even without crossreferenced default arguments.

Best wishes,

Matthias


Von: S Ellison
Gesendet: Dienstag, 5. September 2017 16:17
An: Matthias Gondan; r-help@r-project.org
Betreff: RE: [R] Strange lazy evaluation of default arguments

Mathias,
If it's any comfort, I appreciated the example; 'expected' behaviour maybe, but 
a very nice example for staff/student training!

S Ellison


> -Original Message-
> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Matthias
> Gondan
> Sent: 02 September 2017 18:22
> To: r-help@r-project.org
> Subject: [R] Strange lazy evaluation of default arguments
> 
> Dear R developers,
> 
> sessionInfo() below
> 
> Please have a look at the following two versions of the same function:
> 
> 1. Intended behavior:
> 
> > Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
> + {
> +   print(c(u, l, mu)) # here, l is set to u’s value
> +   u = u/sqrt(sigma2)
> +   l = l/sqrt(sigma2)
> +   mu = mu/sqrt(sigma2)
> +   print(c(u, l, mu))
> + }
> >
> > Su1()
> [1] 100.00 100.00   0.53
> [1] 23.2558140 23.2558140  0.1232558
> 
> In the first version, both u and l are correctly divided by 4.3.
> 
> 2. Strange behavior:
> 
> > Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
> + {
> +   # print(c(u, l, mu))
> +   u = u/sqrt(sigma2)
> +   l = l/sqrt(sigma2) # here, l is set to u’s value
> +   mu = mu/sqrt(sigma2)
> +   print(c(u, l, mu))
> + }
> >
> > Su2()
> [1] 23.2558140  5.4083288  0.1232558
> In the second version, the print function is commented out, so the variable u
> is copied to l (lowercase L) at a later place, and L is divided twice by 4.3.
> 
> Is this behavior intended? It seems strange that the result depends on a
> debugging message.
> 
> Best wishes,
> 
> Matthias
> 
> 
> > sessionInfo()
> R version 3.4.1 (2017-06-30)
> Platform: x86_64-w64-mingw32/x64 (64-bit) Running under: Windows >= 8
> x64 (build 9200)
> 
> Matrix products: default
> 
> locale:
> [1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252
> LC_MONETARY=German_Germany.1252
> [4] LC_NUMERIC=CLC_TIME=German_Germany.1252
> 
> attached base packages:
> [1] stats graphics  grDevices utils datasets  methods   base
> 
> loaded via a namespace (and not attached):
> [1] compiler_3.4.1 tools_3.4.1
> 
> 
>   [[alternative HTML version deleted]]
> 
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.


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Re: [R] Strange lazy evaluation of default arguments

2017-09-05 Thread S Ellison

Mathias,
If it's any comfort, I appreciated the example; 'expected' behaviour maybe, but 
a very nice example for staff/student training!

S Ellison


> -Original Message-
> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Matthias
> Gondan
> Sent: 02 September 2017 18:22
> To: r-help@r-project.org
> Subject: [R] Strange lazy evaluation of default arguments
> 
> Dear R developers,
> 
> sessionInfo() below
> 
> Please have a look at the following two versions of the same function:
> 
> 1. Intended behavior:
> 
> > Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
> + {
> +   print(c(u, l, mu)) # here, l is set to u’s value
> +   u = u/sqrt(sigma2)
> +   l = l/sqrt(sigma2)
> +   mu = mu/sqrt(sigma2)
> +   print(c(u, l, mu))
> + }
> >
> > Su1()
> [1] 100.00 100.00   0.53
> [1] 23.2558140 23.2558140  0.1232558
> 
> In the first version, both u and l are correctly divided by 4.3.
> 
> 2. Strange behavior:
> 
> > Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
> + {
> +   # print(c(u, l, mu))
> +   u = u/sqrt(sigma2)
> +   l = l/sqrt(sigma2) # here, l is set to u’s value
> +   mu = mu/sqrt(sigma2)
> +   print(c(u, l, mu))
> + }
> >
> > Su2()
> [1] 23.2558140  5.4083288  0.1232558
> In the second version, the print function is commented out, so the variable u
> is copied to l (lowercase L) at a later place, and L is divided twice by 4.3.
> 
> Is this behavior intended? It seems strange that the result depends on a
> debugging message.
> 
> Best wishes,
> 
> Matthias
> 
> 
> > sessionInfo()
> R version 3.4.1 (2017-06-30)
> Platform: x86_64-w64-mingw32/x64 (64-bit) Running under: Windows >= 8
> x64 (build 9200)
> 
> Matrix products: default
> 
> locale:
> [1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252
> LC_MONETARY=German_Germany.1252
> [4] LC_NUMERIC=CLC_TIME=German_Germany.1252
> 
> attached base packages:
> [1] stats graphics  grDevices utils datasets  methods   base
> 
> loaded via a namespace (and not attached):
> [1] compiler_3.4.1 tools_3.4.1
> 
> 
>   [[alternative HTML version deleted]]
> 
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.


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Re: [R] Strange lazy evaluation of default arguments

2017-09-02 Thread Bert Gunter

This is exactly as expected. See section 4.3.3 of the R Language definition
or google around on "R Lazy Evaluation" for details.

You should not "expect" R's semantics to be the same as other languages
with which you may be familiar. Spending time with a good tutorial or two
should help you sort out points of similarity and differences.

Cheers,
Bert



Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Sat, Sep 2, 2017 at 10:22 AM, Matthias Gondan 
wrote:

> Dear R developers,
>
> sessionInfo() below
>
> Please have a look at the following two versions of the same function:
>
> 1. Intended behavior:
>
> > Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
> + {
> +   print(c(u, l, mu)) # here, l is set to u’s value
> +   u = u/sqrt(sigma2)
> +   l = l/sqrt(sigma2)
> +   mu = mu/sqrt(sigma2)
> +   print(c(u, l, mu))
> + }
> >
> > Su1()
> [1] 100.00 100.00   0.53
> [1] 23.2558140 23.2558140  0.1232558
>
> In the first version, both u and l are correctly divided by 4.3.
>
> 2. Strange behavior:
>
> > Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
> + {
> +   # print(c(u, l, mu))
> +   u = u/sqrt(sigma2)
> +   l = l/sqrt(sigma2) # here, l is set to u’s value
> +   mu = mu/sqrt(sigma2)
> +   print(c(u, l, mu))
> + }
> >
> > Su2()
> [1] 23.2558140  5.4083288  0.1232558
> In the second version, the print function is commented out, so the
> variable u is
> copied to l (lowercase L) at a later place, and L is divided twice by 4.3.
>
> Is this behavior intended? It seems strange that the result depends on a
> debugging message.
>
> Best wishes,
>
> Matthias
>
>
> > sessionInfo()
> R version 3.4.1 (2017-06-30)
> Platform: x86_64-w64-mingw32/x64 (64-bit)
> Running under: Windows >= 8 x64 (build 9200)
>
> Matrix products: default
>
> locale:
> [1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252
> LC_MONETARY=German_Germany.1252
> [4] LC_NUMERIC=CLC_TIME=German_Germany.1252
>
> attached base packages:
> [1] stats graphics  grDevices utils datasets  methods   base
>
> loaded via a namespace (and not attached):
> [1] compiler_3.4.1 tools_3.4.1
>
>
> [[alternative HTML version deleted]]
>
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/
> posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

[[alternative HTML version deleted]]

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Re: [R] Strange lazy evaluation of default arguments

2017-09-02 Thread Jeff Newmiller

Yes, this is intended behavior, and it has everything to do with where the 
parameters are first referenced and nothing to do with debugging. 
-- 
Sent from my phone. Please excuse my brevity.

On September 2, 2017 10:22:22 AM PDT, Matthias Gondan  
wrote:
>Dear R developers,
>
>sessionInfo() below
>
>Please have a look at the following two versions of the same function:
>
>1. Intended behavior:
>
>> Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
>+ {
>+   print(c(u, l, mu)) # here, l is set to u’s value
>+   u = u/sqrt(sigma2)
>+   l = l/sqrt(sigma2)
>+   mu = mu/sqrt(sigma2)
>+   print(c(u, l, mu))
>+ }
>> 
>> Su1()
>[1] 100.00 100.00   0.53
>[1] 23.2558140 23.2558140  0.1232558
>
>In the first version, both u and l are correctly divided by 4.3.
>
>2. Strange behavior:
>
>> Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
>+ {
>+   # print(c(u, l, mu))
>+   u = u/sqrt(sigma2)
>+   l = l/sqrt(sigma2) # here, l is set to u’s value
>+   mu = mu/sqrt(sigma2)
>+   print(c(u, l, mu))
>+ }
>> 
>> Su2()
>[1] 23.2558140  5.4083288  0.1232558>In the second version, the print
>function is commented out, so the variable u is 
>copied to l (lowercase L) at a later place, and L is divided twice by
>4.3.
>
>Is this behavior intended? It seems strange that the result depends on
>a debugging message.
>
>Best wishes,
>
>Matthias sessionInfo()
>R version 3.4.1 (2017-06-30)
>Platform: x86_64-w64-mingw32/x64 (64-bit)
>Running under: Windows >= 8 x64 (build 9200)
>
>Matrix products: default
>
>locale:
>[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252   
>LC_MONETARY=German_Germany.1252
>[4] LC_NUMERIC=CLC_TIME=German_Germany.1252
>
>attached base packages:
>[1] stats graphics  grDevices utils datasets  methods   base   
> 
>
>loaded via a namespace (and not attached):
>[1] compiler_3.4.1 tools_3.4.1   
>
>
>   [[alternative HTML version deleted]]
>
>__
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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Re: [R] Strange lazy evaluation of default arguments

2017-09-02 Thread Matthias Gondan

Dear Bill,

All makes perfect sense (including the late evaluation). I actually discovered 
the problem by looking at old code which used your proposed solution. Still I 
find it strange (and, hnestly, I don’t like R’s behavior in this respect), and 
I am wondering why u is not being copied to L just before u is assigned a new 
value. Of course, this would require the R interpreter to track all these 
dependencies in both ways incl. more complicated ones in which L might depend 
on more than just u.

In the future, I’ll avoid dependencies between parameters.

Su4 <- function(u=100, l=100, mu=0.53, sigma2=4.3^2) # instead of l=u

And maybe also „in-place“ changes of values…

Best regards,

Matthias

Von: William Dunlap
Gesendet: Samstag, 2. September 2017 19:41
An: Rui Barradas
Cc: Matthias Gondan; r-help@r-project.org
Betreff: Re: [R] Strange lazy evaluation of default arguments

Another way to avoid the problem is to not redefine variables that are 
arguments.  E.g.,

> Su3 <- function(u=100, l=u, mu=0.53, sigma2=4.3^2, verbose)
  {
    if (verbose) {
      print(c(u, l, mu))
    }
    uNormalized <- u/sqrt(sigma2)
    lNormalized <- l/sqrt(sigma2)
    muNormalized <- mu/sqrt(sigma2)
    c(uNormalized, lNormalized, muNormalized)
  }
> Su3(verbose=TRUE)
[1] 100.00 100.00   0.53
[1] 23.2558140 23.2558140  0.1232558
> Su3(verbose=FALSE)
[1] 23.2558140 23.2558140  0.1232558

Not redefining variables at all makes debugging easier, although it may waste 
space.

Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Sat, Sep 2, 2017 at 10:33 AM, <ruipbarra...@sapo.pt> wrote:
Hello,

One way of preventing that is to use ?force.
Just put

   force(l)

right after the commented out print and before you change 'u'.

Hope this helps,

Rui Barradas

Citando Matthias Gondan <matthias-gon...@gmx.de>:

Dear R developers,

sessionInfo() below

Please have a look at the following two versions of the same function:

1. Intended behavior:
Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
+ {
+   print(c(u, l, mu)) # here, l is set to u’s value
+   u = u/sqrt(sigma2)
+   l = l/sqrt(sigma2)
+   mu = mu/sqrt(sigma2)
+   print(c(u, l, mu))
+ }

Su1()
[1] 100.00 100.00   0.53
[1] 23.2558140 23.2558140  0.1232558

In the first version, both u and l are correctly divided by 4.3.

2. Strange behavior:
Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
+ {
+   # print(c(u, l, mu))
+   u = u/sqrt(sigma2)
+   l = l/sqrt(sigma2) # here, l is set to u’s value
+   mu = mu/sqrt(sigma2)
+   print(c(u, l, mu))
+ }

Su2()
[1] 23.2558140  5.4083288  0.1232558
In the second version, the print
function is commented out, so the variable u is
copied to l (lowercase L) at a later place, and L is divided twice by 4.3.

Is this behavior intended? It seems strange that the result depends on a 
debugging message.

Best wishes,

Matthias

sessionInfo()
R version 3.4.1 (2017-06-30)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

Matrix products: default

locale:
[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252    
LC_MONETARY=German_Germany.1252
[4] LC_NUMERIC=C                    LC_TIME=German_Germany.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] compiler_3.4.1 tools_3.4.1

        [[alternative HTML version deleted]]

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and provide commented, minimal, self-contained, reproducible code.

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Re: [R] Strange lazy evaluation of default arguments

2017-09-02 Thread William Dunlap via R-help

Another way to avoid the problem is to not redefine variables that are
arguments.  E.g.,

> Su3 <- function(u=100, l=u, mu=0.53, sigma2=4.3^2, verbose)
  {
if (verbose) {
  print(c(u, l, mu))
}
uNormalized <- u/sqrt(sigma2)
lNormalized <- l/sqrt(sigma2)
muNormalized <- mu/sqrt(sigma2)
c(uNormalized, lNormalized, muNormalized)
  }
> Su3(verbose=TRUE)
[1] 100.00 100.00   0.53
[1] 23.2558140 23.2558140  0.1232558
> Su3(verbose=FALSE)
[1] 23.2558140 23.2558140  0.1232558

Not redefining variables at all makes debugging easier, although it may
waste space.

Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Sat, Sep 2, 2017 at 10:33 AM,  wrote:

> Hello,
>
> One way of preventing that is to use ?force.
> Just put
>
>force(l)
>
> right after the commented out print and before you change 'u'.
>
> Hope this helps,
>
> Rui Barradas
>
>
>
> Citando Matthias Gondan :
>
>
> Dear R developers,
>>
>> sessionInfo() below
>>
>> Please have a look at the following two versions of the same function:
>>
>> 1. Intended behavior:
>>
>> Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
>>>
>> + {
>> +   print(c(u, l, mu)) # here, l is set to u’s value
>> +   u = u/sqrt(sigma2)
>> +   l = l/sqrt(sigma2)
>> +   mu = mu/sqrt(sigma2)
>> +   print(c(u, l, mu))
>> + }
>>
>>>
>>> Su1()
>>>
>> [1] 100.00 100.00   0.53
>> [1] 23.2558140 23.2558140  0.1232558
>>
>> In the first version, both u and l are correctly divided by 4.3.
>>
>> 2. Strange behavior:
>>
>> Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)
>>>
>> + {
>> +   # print(c(u, l, mu))
>> +   u = u/sqrt(sigma2)
>> +   l = l/sqrt(sigma2) # here, l is set to u’s value
>> +   mu = mu/sqrt(sigma2)
>> +   print(c(u, l, mu))
>> + }
>>
>>>
>>> Su2()
>>>
>> [1] 23.2558140  5.4083288  0.1232558
>>
> In the second version, the print
>
>> function is commented out, so the variable u is
>> copied to l (lowercase L) at a later place, and L is divided twice by 4.3.
>>
>> Is this behavior intended? It seems strange that the result depends on a
>> debugging message.
>>
>> Best wishes,
>>
>> Matthias
>>
>
>
> sessionInfo()
>> R version 3.4.1 (2017-06-30)
>> Platform: x86_64-w64-mingw32/x64 (64-bit)
>> Running under: Windows >= 8 x64 (build 9200)
>>
>> Matrix products: default
>>
>> locale:
>> [1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252
>> LC_MONETARY=German_Germany.1252
>> [4] LC_NUMERIC=CLC_TIME=German_Germany.1252
>>
>> attached base packages:
>> [1] stats graphics  grDevices utils datasets  methods   base
>>
>> loaded via a namespace (and not attached):
>> [1] compiler_3.4.1 tools_3.4.1
>>
>>
>> [[alternative HTML version deleted]]
>>
>> __
>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posti
>> ng-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posti
> ng-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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Re: [R] Strange lazy evaluation of default arguments

2017-09-02 Thread ruipbarradas


Hello,

One way of preventing that is to use ?force.
Just put

   force(l)

right after the commented out print and before you change 'u'.

Hope this helps,

Rui Barradas



Citando Matthias Gondan :


Dear R developers,

sessionInfo() below

Please have a look at the following two versions of the same function:

1. Intended behavior:


Su1 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)

+ {
+   print(c(u, l, mu)) # here, l is set to u’s value
+   u = u/sqrt(sigma2)
+   l = l/sqrt(sigma2)
+   mu = mu/sqrt(sigma2)
+   print(c(u, l, mu))
+ }


Su1()

[1] 100.00 100.00   0.53
[1] 23.2558140 23.2558140  0.1232558

In the first version, both u and l are correctly divided by 4.3.

2. Strange behavior:


Su2 = function(u=100, l=u, mu=0.53, sigma2=4.3^2)

+ {
+   # print(c(u, l, mu))
+   u = u/sqrt(sigma2)
+   l = l/sqrt(sigma2) # here, l is set to u’s value
+   mu = mu/sqrt(sigma2)
+   print(c(u, l, mu))
+ }


Su2()

[1] 23.2558140  5.4083288  0.1232558

In the second version, the print

function is commented out, so the variable u is
copied to l (lowercase L) at a later place, and L is divided twice by 4.3.

Is this behavior intended? It seems strange that the result depends  
on a debugging message.


Best wishes,

Matthias




sessionInfo()
R version 3.4.1 (2017-06-30)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

Matrix products: default

locale:
[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252 
LC_MONETARY=German_Germany.1252

[4] LC_NUMERIC=CLC_TIME=German_Germany.1252

attached base packages:
[1] stats graphics  grDevices utils datasets  methods   base

loaded via a namespace (and not attached):
[1] compiler_3.4.1 tools_3.4.1


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R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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and provide commented, minimal, self-contained, reproducible code.


__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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Re: [R] Strange lazy evaluation of default arguments

Re: [R] Strange lazy evaluation of default arguments

Re: [R] Strange lazy evaluation of default arguments

Re: [R] Strange lazy evaluation of default arguments

Re: [R] Strange lazy evaluation of default arguments

Re: [R] Strange lazy evaluation of default arguments

Re: [R] Strange lazy evaluation of default arguments

Re: [R] Strange lazy evaluation of default arguments

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