Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Wed, Jun 08, 2011 at 08:35:34PM -0400, Simon Urbanek wrote:
On Jun 8, 2011, at 8:32 PM, oliver wrote:
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote:
[...]
OK, I looked at this now.
LENGTH() checks the length of the vector.
Good to know this.
So the problem of a vector of length 0 can be with any arguments of type
SEXP,
hence I will need to check ANY arg on it's length.
This is vital to stability under any situation.
Thanks for this valuable hint!
I will add checks for all my SEXP-args.
[...]
Hey, LENGTH() does not work with String-vectors! :(
Of course it does ...
It does not so on my R 2.10.1 installation.
In the R-Shell I get:
==
length(c())
[1] 0
==
So c() is vec of length 0.
When I feed my readjpeg() with c() as filename arg,
testing with:
if( LENGTH( filename_sexp ) 1 )
{
error(LENGTH( filename_sexp ) 1);
//error(filename can't be vector of length 0);
}
else
{
error(LENGTH( filename_sexp ) is not 1);
}
I got:
Error in readjpeg(filename = c()) : LENGTH( filename_sexp ) is not 1
You can explain why?
Ciao,
Oliver
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On 11-06-09 7:27 AM, oliver wrote:
On Wed, Jun 08, 2011 at 08:35:34PM -0400, Simon Urbanek wrote:
On Jun 8, 2011, at 8:32 PM, oliver wrote:
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote:
[...]
OK, I looked at this now.
LENGTH() checks the length of the vector.
Good to know this.
So the problem of a vector of length 0 can be with any arguments of type SEXP,
hence I will need to check ANY arg on it's length.
This is vital to stability under any situation.
Thanks for this valuable hint!
I will add checks for all my SEXP-args.
[...]
Hey, LENGTH() does not work with String-vectors! :(
Of course it does ...
It does not so on my R 2.10.1 installation.
In the R-Shell I get:
==
length(c())
[1] 0
==
So c() is vec of length 0.
When I feed my readjpeg() with c() as filename arg,
testing with:
if( LENGTH( filename_sexp ) 1 )
{
error(LENGTH( filename_sexp ) 1);
//error(filename can't be vector of length 0);
}
else
{
error(LENGTH( filename_sexp ) is not 1);
}
I got:
Error in readjpeg(filename = c()) : LENGTH( filename_sexp ) is not 1
You can explain why?
c() doesn't create a STRSXP, it is NULL, which is a NILSXP. LENGTH()
doesn't work on that object. (I'd recommend using length() rather than
LENGTH(); it's a function, not a macro, and it does give the expected
answer.)
Duncan Murdoch
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Thu, Jun 09, 2011 at 07:43:20AM -0400, Duncan Murdoch wrote:
On 11-06-09 7:27 AM, oliver wrote:
On Wed, Jun 08, 2011 at 08:35:34PM -0400, Simon Urbanek wrote:
On Jun 8, 2011, at 8:32 PM, oliver wrote:
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote:
[...]
OK, I looked at this now.
LENGTH() checks the length of the vector.
Good to know this.
So the problem of a vector of length 0 can be with any arguments of type
SEXP,
hence I will need to check ANY arg on it's length.
This is vital to stability under any situation.
Thanks for this valuable hint!
I will add checks for all my SEXP-args.
[...]
Hey, LENGTH() does not work with String-vectors! :(
Of course it does ...
It does not so on my R 2.10.1 installation.
In the R-Shell I get:
==
length(c())
[1] 0
==
So c() is vec of length 0.
When I feed my readjpeg() with c() as filename arg,
testing with:
if( LENGTH( filename_sexp ) 1 )
{
error(LENGTH( filename_sexp ) 1);
//error(filename can't be vector of length 0);
}
else
{
error(LENGTH( filename_sexp ) is not 1);
}
I got:
Error in readjpeg(filename = c()) : LENGTH( filename_sexp ) is not 1
You can explain why?
c() doesn't create a STRSXP, it is NULL, which is a NILSXP.
LENGTH() doesn't work on that object. (I'd recommend using length()
rather than LENGTH(); it's a function, not a macro, and it does give
the expected answer.)
[...]
Interestingly, c() as value for an integer value
can be testes correctly with LENGTH().
So the question arises: is c() always creating NILSXP,
or is it NILSXP only for STRSXP, and 0 otherwise?
NILSXP, as it might be close to a NULL might be interpreted as 0
length by LENGTH...
Nevertheless it's a littlebid confusing for people who don't know the
internals of R.
Will try length() soon.
Ciao,
Oliver
P.S.: To be picky: NOT knowing the internals and nevertheless using the
available
functions/macros is called encapsulation in OO or the difference between
interface and implementation... which is good style of programming.
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On 09/06/2011 9:28 AM, oliver wrote:
On Thu, Jun 09, 2011 at 07:43:20AM -0400, Duncan Murdoch wrote:
On 11-06-09 7:27 AM, oliver wrote:
On Wed, Jun 08, 2011 at 08:35:34PM -0400, Simon Urbanek wrote:
On Jun 8, 2011, at 8:32 PM, oliver wrote:
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote:
[...]
OK, I looked at this now.
LENGTH() checks the length of the vector.
Good to know this.
So the problem of a vector of length 0 can be with any arguments of type
SEXP,
hence I will need to check ANY arg on it's length.
This is vital to stability under any situation.
Thanks for this valuable hint!
I will add checks for all my SEXP-args.
[...]
Hey, LENGTH() does not work with String-vectors! :(
Of course it does ...
It does not so on my R 2.10.1 installation.
In the R-Shell I get:
==
length(c())
[1] 0
==
So c() is vec of length 0.
When I feed my readjpeg() with c() as filename arg,
testing with:
if( LENGTH( filename_sexp ) 1 )
{
error(LENGTH( filename_sexp ) 1);
//error(filename can't be vector of length 0);
}
else
{
error(LENGTH( filename_sexp ) is not 1);
}
I got:
Error in readjpeg(filename = c()) : LENGTH( filename_sexp ) is not 1
You can explain why?
c() doesn't create a STRSXP, it is NULL, which is a NILSXP.
LENGTH() doesn't work on that object. (I'd recommend using length()
rather than LENGTH(); it's a function, not a macro, and it does give
the expected answer.)
[...]
Interestingly, c() as value for an integer value
can be testes correctly with LENGTH().
Presumably you converted it to an INTSXP. c() is NULL.
So the question arises: is c() always creating NILSXP,
or is it NILSXP only for STRSXP, and 0 otherwise?
That question makes no sense at all.
Duncan Murdoch
NILSXP, as it might be close to a NULL might be interpreted as 0
length by LENGTH...
Nevertheless it's a littlebid confusing for people who don't know the
internals of R.
Will try length() soon.
Ciao,
Oliver
P.S.: To be picky: NOT knowing the internals and nevertheless using the
available
functions/macros is called encapsulation in OO or the difference between
interface and implementation... which is good style of programming.
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Thu, Jun 09, 2011 at 10:54:28AM -0400, Duncan Murdoch wrote:
On 09/06/2011 9:28 AM, oliver wrote:
On Thu, Jun 09, 2011 at 07:43:20AM -0400, Duncan Murdoch wrote:
On 11-06-09 7:27 AM, oliver wrote:
On Wed, Jun 08, 2011 at 08:35:34PM -0400, Simon Urbanek wrote:
On Jun 8, 2011, at 8:32 PM, oliver wrote:
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote:
[...]
OK, I looked at this now.
LENGTH() checks the length of the vector.
Good to know this.
So the problem of a vector of length 0 can be with any arguments of
type SEXP,
hence I will need to check ANY arg on it's length.
This is vital to stability under any situation.
Thanks for this valuable hint!
I will add checks for all my SEXP-args.
[...]
Hey, LENGTH() does not work with String-vectors! :(
Of course it does ...
It does not so on my R 2.10.1 installation.
In the R-Shell I get:
==
length(c())
[1] 0
==
So c() is vec of length 0.
When I feed my readjpeg() with c() as filename arg,
testing with:
if( LENGTH( filename_sexp ) 1 )
{
error(LENGTH( filename_sexp ) 1);
//error(filename can't be vector of length 0);
}
else
{
error(LENGTH( filename_sexp ) is not 1);
}
I got:
Error in readjpeg(filename = c()) : LENGTH( filename_sexp ) is not
1
You can explain why?
c() doesn't create a STRSXP, it is NULL, which is a NILSXP.
LENGTH() doesn't work on that object. (I'd recommend using length()
rather than LENGTH(); it's a function, not a macro, and it does give
the expected answer.)
[...]
Interestingly, c() as value for an integer value
can be testes correctly with LENGTH().
Presumably you converted it to an INTSXP. c() is NULL.
[...]
Ooops, yes. In the R-part. :-)
I did it, because when I don't get an int from the user's call,
I have set it to NA (default in the R-function definition).
I made
width - as.integer(width)
for easy check inside the C-part, on integer.
(I really only need int, no floating point values.)
I thought this makes the C-code easier at that part.
Or I may check on NA inside the C-part.
How would I do that correctly?
After so much different opinions I read here, I'm rather puzzled on that now.
If there is already a R-extensions-FAQ I could collect the informations
from the mail sof the last days, so that the different opinions and the
discussion
can result in a some answers...
So the question arises: is c() always creating NILSXP,
or is it NILSXP only for STRSXP, and 0 otherwise?
That question makes no sense at all.
It make sense for the picky.
As NULL is rather (void*)0 and a pointer is not an int (just can be coerced
normally) ;)
Ciao,
Oliver
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Jun 9, 2011, at 11:15 AM, oliver wrote:
On Thu, Jun 09, 2011 at 10:54:28AM -0400, Duncan Murdoch wrote:
On 09/06/2011 9:28 AM, oliver wrote:
On Thu, Jun 09, 2011 at 07:43:20AM -0400, Duncan Murdoch wrote:
On 11-06-09 7:27 AM, oliver wrote:
On Wed, Jun 08, 2011 at 08:35:34PM -0400, Simon Urbanek wrote:
On Jun 8, 2011, at 8:32 PM, oliver wrote:
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote:
[...]
OK, I looked at this now.
LENGTH() checks the length of the vector.
Good to know this.
So the problem of a vector of length 0 can be with any arguments of
type SEXP,
hence I will need to check ANY arg on it's length.
This is vital to stability under any situation.
Thanks for this valuable hint!
I will add checks for all my SEXP-args.
[...]
Hey, LENGTH() does not work with String-vectors! :(
Of course it does ...
It does not so on my R 2.10.1 installation.
In the R-Shell I get:
==
length(c())
[1] 0
==
So c() is vec of length 0.
When I feed my readjpeg() with c() as filename arg,
testing with:
if( LENGTH( filename_sexp ) 1 )
{
error(LENGTH( filename_sexp ) 1);
//error(filename can't be vector of length 0);
}
else
{
error(LENGTH( filename_sexp ) is not 1);
}
I got:
Error in readjpeg(filename = c()) : LENGTH( filename_sexp ) is not 1
You can explain why?
c() doesn't create a STRSXP, it is NULL, which is a NILSXP.
LENGTH() doesn't work on that object. (I'd recommend using length()
rather than LENGTH(); it's a function, not a macro, and it does give
the expected answer.)
[...]
Interestingly, c() as value for an integer value
can be testes correctly with LENGTH().
Presumably you converted it to an INTSXP. c() is NULL.
[...]
Ooops, yes. In the R-part. :-)
I did it, because when I don't get an int from the user's call,
I have set it to NA (default in the R-function definition).
I made
width - as.integer(width)
for easy check inside the C-part, on integer.
(I really only need int, no floating point values.)
I thought this makes the C-code easier at that part.
Or I may check on NA inside the C-part.
How would I do that correctly?
After so much different opinions I read here, I'm rather puzzled on that now.
If there is already a R-extensions-FAQ I could collect the informations
from the mail sof the last days, so that the different opinions and the
discussion
can result in a some answers...
So far you were creating the confusion, the facts are fairly simple if you have
some clue about C and R. I would like to ask you to, please, read and
understand C standard and R-exts *before* posting further questions since it's
pointless if we provide answers that you don't understand. The fact that you
are impatient (as you said yourself) doesn't entitle you to waste other
people's time to explain things to you while you are unwilling to take the time
yourself. If you have serious question beyond what is documented, feel free to
ask, but make sure you have spent the time to think about it before you do so.
So the question arises: is c() always creating NILSXP,
or is it NILSXP only for STRSXP, and 0 otherwise?
That question makes no sense at all.
It make sense for the picky.
As NULL is rather (void*)0 and a pointer is not an int (just can be coerced
normally) ;)
It's not - you're confusing NULL in R with NULL in C.
Both NILSXP and STRSXP are SEXP types - and obviously distinct ones. R will
never return a null pointer for a SEXP.
Cheers,
Simon
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Thu, Jun 09, 2011 at 12:56:09PM -0400, Simon Urbanek wrote:
On Jun 9, 2011, at 11:15 AM, oliver wrote:
On Thu, Jun 09, 2011 at 10:54:28AM -0400, Duncan Murdoch wrote:
On 09/06/2011 9:28 AM, oliver wrote:
On Thu, Jun 09, 2011 at 07:43:20AM -0400, Duncan Murdoch wrote:
On 11-06-09 7:27 AM, oliver wrote:
On Wed, Jun 08, 2011 at 08:35:34PM -0400, Simon Urbanek wrote:
On Jun 8, 2011, at 8:32 PM, oliver wrote:
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote:
[...]
OK, I looked at this now.
LENGTH() checks the length of the vector.
Good to know this.
So the problem of a vector of length 0 can be with any arguments of
type SEXP,
hence I will need to check ANY arg on it's length.
This is vital to stability under any situation.
Thanks for this valuable hint!
I will add checks for all my SEXP-args.
[...]
Hey, LENGTH() does not work with String-vectors! :(
Of course it does ...
It does not so on my R 2.10.1 installation.
In the R-Shell I get:
==
length(c())
[1] 0
==
So c() is vec of length 0.
When I feed my readjpeg() with c() as filename arg,
testing with:
if( LENGTH( filename_sexp ) 1 )
{
error(LENGTH( filename_sexp ) 1);
//error(filename can't be vector of length 0);
}
else
{
error(LENGTH( filename_sexp ) is not 1);
}
I got:
Error in readjpeg(filename = c()) : LENGTH( filename_sexp ) is not
1
You can explain why?
c() doesn't create a STRSXP, it is NULL, which is a NILSXP.
LENGTH() doesn't work on that object. (I'd recommend using length()
rather than LENGTH(); it's a function, not a macro, and it does give
the expected answer.)
[...]
Interestingly, c() as value for an integer value
can be testes correctly with LENGTH().
Presumably you converted it to an INTSXP. c() is NULL.
[...]
Ooops, yes. In the R-part. :-)
I did it, because when I don't get an int from the user's call,
I have set it to NA (default in the R-function definition).
I made
width - as.integer(width)
for easy check inside the C-part, on integer.
(I really only need int, no floating point values.)
I thought this makes the C-code easier at that part.
Or I may check on NA inside the C-part.
How would I do that correctly?
After so much different opinions I read here, I'm rather puzzled on that
now.
If there is already a R-extensions-FAQ I could collect the informations
from the mail sof the last days, so that the different opinions and the
discussion
can result in a some answers...
So far you were creating the confusion, the facts are fairly simple if you
have some clue about C and R. I would like to ask you to, please, read and
understand C standard and R-exts *before* posting further questions since it's
pointless if we provide answers that you don't understand.
[...]
I understand the answers if it's about C, but I'm new to R.
If you think I did wrote something about C, that is not correct,
please show me.
On the R-usage: Regarding the LENGTH() vs. length(),
both are used in the examples of Writing R Extensions
and somewhere it was mentioned that either macros or functions can be used.
Here on the list I read different opinions about that, coming from different
people.
As there are also different usages in the Writing R Extensions it's confusing.
Macro or function?
Should I include Rinternals.h or Rdefines.h?
It's not clear, what I should prefer, or when.
The fact that you
are impatient (as you said yourself) doesn't entitle you to waste other
people's time to explain things to you while you are unwilling to take the
time
yourself.
That the memory allocation part was coming in chapter six,
which at first glance rather looked like a reference of convenience or
mathematical
functions that can be called, I didn't awaited.
(And so I missed it in chapter 5, hence my questions.)
So I just can apologize that I didn't read that before asking,
but also can mention that the memory allocation issue also might make sense to
be
mentioned in chapter 5.
And on the other hand I think wasting time of others makes no sense.
I also would invest time to help others on topics, even it might be documented
somewhere. (Thats why there are mailing lists, IMHO.)
It could even be the case that people read something but didn't remember
anything after first reading.
For example I had to look at the Writing R extensions more than once,
and some things I already read, I had not saved immediately.
(That's normal, that people need repitition to learn, btw.)
There always is a tradeoff between first-read-long-documentations and do not
practice
and read in the docs, try it out, read more,
Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Tue, 7 Jun 2011, Duncan Murdoch wrote:
On 07/06/2011 9:08 AM, oliver wrote:
Hello,
following an advice here from the list I looked into sources of other
packages (xts) and found the TYPEOF() macro/function, which really is
helpful.
It is documented, of course, but actually better alternatives are
described in 'Writing R Extensions'.
We would urge you to study the R sources rather than copy bad habits
from randomly chosen package sources.
I iused the follwong code snippet:
switch( TYPEOF( filename_sexp ) )
{
case STRSXP: filename = CHAR( STRING_ELT(filename_sexp, 0) );
break;
default: error(filename argument must be a string);
break;
}
Here, filename is of type char*
and one function opens a file with that name.
So it is purely intended to just grab out the char* from the
String-Expression.
Am I doing something wrong here, or is it ok, but I have somehow
to say the extracting macros/functions, that it is really intended
to throw away information and that a warning is not necessary?
The result of calling CHAR should be a const char *. You are not allowed
to touch the string it points to.
Note too that isString() exists for this purpose, and there is no
check in that code that LENGTH(filename_sexp) 0 (or == 1). In the R
sources you will often see things like
if(!isString(sfile) || LENGTH(sfile) 1)
error(invalid '%s' argument, description);
Then, reading on,
file = translateChar(STRING_ELT(sfile, 0));
for you cannot (in general) assume that the character vector passed is
in the native encoding.
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UKFax: +44 1865 272595
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Wed, Jun 08, 2011 at 12:22:10PM +0100, Prof Brian Ripley wrote:
On Tue, 7 Jun 2011, Duncan Murdoch wrote:
On 07/06/2011 9:08 AM, oliver wrote:
Hello,
following an advice here from the list I looked into sources of other
packages (xts) and found the TYPEOF() macro/function, which really is
helpful.
It is documented, of course, but actually better alternatives are
described in 'Writing R Extensions'.
We would urge you to study the R sources rather than copy bad habits
from randomly chosen package sources.
[...]
Hmhh, it was not randomly chosen, it was, what I got as a hint here on the list.
I iused the follwong code snippet:
switch( TYPEOF( filename_sexp ) )
{
case STRSXP: filename = CHAR( STRING_ELT(filename_sexp, 0) );
break;
default: error(filename argument must be a string);
break;
}
Here, filename is of type char*
and one function opens a file with that name.
So it is purely intended to just grab out the char* from the
String-Expression.
Am I doing something wrong here, or is it ok, but I have somehow
to say the extracting macros/functions, that it is really intended
to throw away information and that a warning is not necessary?
The result of calling CHAR should be a const char *. You are
not allowed to touch the string it points to.
Note too that isString() exists for this purpose,
[...]
OK, I also sometimes used that (maybe I threw it out or used it in other
modules).
and there is no
check in that code that LENGTH(filename_sexp) 0 (or == 1). In the
R sources you will often see things like
if(!isString(sfile) || LENGTH(sfile) 1)
error(invalid '%s' argument, description);
[...]
If it's a vector, I can just pic the first element.
Or does LENGTH(sfile) give the length of the string itself
(like strlen(3))?
If the latter, then my file-opeing operation would faile with an error.
Of course I check if my fopen() gibves back NULL.
Then, reading on,
file = translateChar(STRING_ELT(sfile, 0));
translateChar is explained on page 120 of the extension writing do.
I'm not in this point of the documentation.
And I often need to look around, when I want to find a function,
as they are documented/explained somewhere during the flow of the text.
Something like a API description that is brief would help.
For example something like in the manuals of the OCaml language:
http://caml.inria.fr/pub/docs/manual-ocaml/libref/Pervasives.html
That's very brief.
Chapter 6 of the Writing R Extensions is rather in this style
and gives a good overview.
Something like that for the macros would be helpful.
for you cannot (in general) assume that the character vector passed
is in the native encoding.
I try to do some coercions (e.g. as.integer())
when I need integer in the C-code and then
in the C-part rigidly check on integer.
About the char-encodings I have not thought much.
Ciao,
Oliver
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Jun 8, 2011, at 12:08 PM, oliver wrote:
On Wed, Jun 08, 2011 at 12:22:10PM +0100, Prof Brian Ripley wrote:
On Tue, 7 Jun 2011, Duncan Murdoch wrote:
On 07/06/2011 9:08 AM, oliver wrote:
Hello,
following an advice here from the list I looked into sources of other
packages (xts) and found the TYPEOF() macro/function, which really is
helpful.
It is documented, of course, but actually better alternatives are
described in 'Writing R Extensions'.
We would urge you to study the R sources rather than copy bad habits
from randomly chosen package sources.
[...]
Hmhh, it was not randomly chosen, it was, what I got as a hint here on the
list.
It was not provided to you to look at how it checks arguments. For basic usage
it's better to look at the R code. The coding styles vary a lot in packages
(and so does the quality of packages) - some of them are really bad, but you
have to remember that most people write packages in their free time and are not
programmers...
I iused the follwong code snippet:
switch( TYPEOF( filename_sexp ) )
{
case STRSXP: filename = CHAR( STRING_ELT(filename_sexp, 0) );
break;
default: error(filename argument must be a string);
break;
}
Here, filename is of type char*
and one function opens a file with that name.
So it is purely intended to just grab out the char* from the
String-Expression.
Am I doing something wrong here, or is it ok, but I have somehow
to say the extracting macros/functions, that it is really intended
to throw away information and that a warning is not necessary?
The result of calling CHAR should be a const char *. You are
not allowed to touch the string it points to.
Note too that isString() exists for this purpose,
[...]
OK, I also sometimes used that (maybe I threw it out or used it in other
modules).
and there is no
check in that code that LENGTH(filename_sexp) 0 (or == 1). In the
R sources you will often see things like
if(!isString(sfile) || LENGTH(sfile) 1)
error(invalid '%s' argument, description);
[...]
If it's a vector, I can just pic the first element.
Yes, but only if it's not a vector of length zero - hence the necessary check.
Or does LENGTH(sfile) give the length of the string itself
(like strlen(3))?
No.
If the latter, then my file-opeing operation would faile with an error.
Of course I check if my fopen() gibves back NULL.
Then, reading on,
file = translateChar(STRING_ELT(sfile, 0));
translateChar is explained on page 120 of the extension writing do.
I'm not in this point of the documentation.
And I often need to look around, when I want to find a function,
as they are documented/explained somewhere during the flow of the text.
Something like a API description that is brief would help.
For example something like in the manuals of the OCaml language:
http://caml.inria.fr/pub/docs/manual-ocaml/libref/Pervasives.html
That's very brief.
Chapter 6 of the Writing R Extensions is rather in this style
and gives a good overview.
Something like that for the macros would be helpful.
for you cannot (in general) assume that the character vector passed
is in the native encoding.
I try to do some coercions (e.g. as.integer())
when I need integer in the C-code and then
in the C-part rigidly check on integer.
It's usually more efficient to use coerceVector() on the C side since that
guarantees no copy is made for matching types (this matters for passing data,
not so much for passing arguments). You can do either - check on R side or
check on C side, usually you don't need both (but you certainly can).
Cheers,
Simon
About the char-encodings I have not thought much.
Ciao,
Oliver
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Wed, Jun 08, 2011 at 02:23:29PM -0400, Simon Urbanek wrote: On Jun 8, 2011, at 12:08 PM, oliver wrote: On Wed, Jun 08, 2011 at 12:22:10PM +0100, Prof Brian Ripley wrote: On Tue, 7 Jun 2011, Duncan Murdoch wrote: On 07/06/2011 9:08 AM, oliver wrote: Hello, following an advice here from the list I looked into sources of other packages (xts) and found the TYPEOF() macro/function, which really is helpful. It is documented, of course, but actually better alternatives are described in 'Writing R Extensions'. We would urge you to study the R sources rather than copy bad habits from randomly chosen package sources. [...] Hmhh, it was not randomly chosen, it was, what I got as a hint here on the list. It was not provided to you to look at how it checks arguments. For basic usage it's better to look at the R code. The coding styles vary a lot in packages (and so does the quality of packages) - some of them are really bad, but you have to remember that most people write packages in their free time and are not programmers... OK, I see. [...] and there is no check in that code that LENGTH(filename_sexp) 0 (or == 1). In the R sources you will often see things like if(!isString(sfile) || LENGTH(sfile) 1) error(invalid '%s' argument, description); [...] If it's a vector, I can just pic the first element. Yes, but only if it's not a vector of length zero - hence the necessary check. Or does LENGTH(sfile) give the length of the string itself (like strlen(3))? No. [...] OK, I looked at this now. LENGTH() checks the length of the vector. Good to know this. So the problem of a vector of length 0 can be with any arguments of type SEXP, hence I will need to check ANY arg on it's length. This is vital to stability under any situation. Thanks for this valuable hint! I will add checks for all my SEXP-args. Ciao, Oliver __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote: [...] OK, I looked at this now. LENGTH() checks the length of the vector. Good to know this. So the problem of a vector of length 0 can be with any arguments of type SEXP, hence I will need to check ANY arg on it's length. This is vital to stability under any situation. Thanks for this valuable hint! I will add checks for all my SEXP-args. [...] Hey, LENGTH() does not work with String-vectors! :( Ciao, Oliver __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Jun 8, 2011, at 8:32 PM, oliver wrote: On Thu, Jun 09, 2011 at 02:17:31AM +0200, oliver wrote: [...] OK, I looked at this now. LENGTH() checks the length of the vector. Good to know this. So the problem of a vector of length 0 can be with any arguments of type SEXP, hence I will need to check ANY arg on it's length. This is vital to stability under any situation. Thanks for this valuable hint! I will add checks for all my SEXP-args. [...] Hey, LENGTH() does not work with String-vectors! :( Of course it does ... __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] warning: assignment discards qualifiers from pointer target type
On Wed, Jun 8, 2011 at 7:17 PM, oliver oli...@first.in-berlin.de wrote: On Wed, Jun 08, 2011 at 02:23:29PM -0400, Simon Urbanek wrote: On Jun 8, 2011, at 12:08 PM, oliver wrote: On Wed, Jun 08, 2011 at 12:22:10PM +0100, Prof Brian Ripley wrote: On Tue, 7 Jun 2011, Duncan Murdoch wrote: On 07/06/2011 9:08 AM, oliver wrote: Hello, following an advice here from the list I looked into sources of other packages (xts) and found the TYPEOF() macro/function, which really is helpful. It is documented, of course, but actually better alternatives are described in 'Writing R Extensions'. We would urge you to study the R sources rather than copy bad habits from randomly chosen package sources. [...] Hmhh, it was not randomly chosen, it was, what I got as a hint here on the list. It was not provided to you to look at how it checks arguments. For basic usage it's better to look at the R code. The coding styles vary a lot in packages (and so does the quality of packages) - some of them are really bad, but you have to remember that most people write packages in their free time and are not programmers... OK, I see. Of course - most of R core aren't programmers either - whatever that means. Statisticians, mathematicians, etc... ;-) Most contributed packages aren't meant to be case studies in a comp-sci class either, they are meant to solve real world problems - problems that many of us work on daily. That said, I'd also say look to R sources first, but since many things in R core aren't available in the API - you aren't really able to copy the 'best practices' alluded to. And sometimes you've got to bootstrap solutions when the list is otherwise silent. Another reason that you should look outside of R sources in addition to inside of them is that the community code is far more abundant that the core code. Sort of like theory vs. practice - they only teach so much in school. For reference, TYPEOF is straight from R source (of course): http://svn.r-project.org/R/trunk/src/main/subset.c Cheers, Jeff [...] and there is no check in that code that LENGTH(filename_sexp) 0 (or == 1). In the R sources you will often see things like if(!isString(sfile) || LENGTH(sfile) 1) error(invalid '%s' argument, description); [...] If it's a vector, I can just pic the first element. Yes, but only if it's not a vector of length zero - hence the necessary check. Or does LENGTH(sfile) give the length of the string itself (like strlen(3))? No. [...] OK, I looked at this now. LENGTH() checks the length of the vector. Good to know this. So the problem of a vector of length 0 can be with any arguments of type SEXP, hence I will need to check ANY arg on it's length. This is vital to stability under any situation. Thanks for this valuable hint! I will add checks for all my SEXP-args. Ciao, Oliver __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel -- Jeffrey Ryan jeffrey.r...@lemnica.com www.lemnica.com www.esotericR.com [[alternative HTML version deleted]] __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
[Rd] warning: assignment discards qualifiers from pointer target type
Hello,
following an advice here from the list I looked into sources of other
packages (xts) and found the TYPEOF() macro/function, which really is
helpful.
I iused the follwong code snippet:
switch( TYPEOF( filename_sexp ) )
{
case STRSXP: filename = CHAR( STRING_ELT(filename_sexp, 0) );
break;
default: error(filename argument must be a string);
break;
}
Here, filename is of type char*
and one function opens a file with that name.
So it is purely intended to just grab out the char* from the
String-Expression.
Am I doing something wrong here, or is it ok, but I have somehow
to say the extracting macros/functions, that it is really intended
to throw away information and that a warning is not necessary?
Ciao,
Oliver
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Re: [Rd] warning: assignment discards qualifiers from pointer target type
On 07/06/2011 9:08 AM, oliver wrote:
Hello,
following an advice here from the list I looked into sources of other
packages (xts) and found the TYPEOF() macro/function, which really is
helpful.
I iused the follwong code snippet:
switch( TYPEOF( filename_sexp ) )
{
case STRSXP: filename = CHAR( STRING_ELT(filename_sexp, 0) );
break;
default: error(filename argument must be a string);
break;
}
Here, filename is of type char*
and one function opens a file with that name.
So it is purely intended to just grab out the char* from the
String-Expression.
Am I doing something wrong here, or is it ok, but I have somehow
to say the extracting macros/functions, that it is really intended
to throw away information and that a warning is not necessary?
The result of calling CHAR should be a const char *. You are not
allowed to touch the string it points to.
Duncan Murdoch
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