[Rcpp-devel] Bug: replace_last()

[teuder at gmail.com]

Hi, Kevin and Qiang.

After I sent my first post, I realized the problem as you pointed out.

The problem can be resolved by replacing replace_first() and replace_last() to find() and rfind().

-------------------
inline String& replace_first(const char* s, const char* news) {
   RCPP_STRING_DEBUG_2("String::replace_first(const char* = '%s' , const
char* = '%s')", s, news);
   if (is_na()) return *this;
   setBuffer();
   size_t index = buffer.find(s);
   //size_t index = buffer.find_first_of(s);
   if (index != std::string::npos) buffer.replace(index, strlen(s), news);
   valid = false;
   return *this;
}

inline String& replace_last(const char* s, const char* news) {
   RCPP_STRING_DEBUG_2("String::replace_last(const char* = '%s' , const
char* = '%s')", s, news);
   if (is_na()) return *this;
   setBuffer();
   size_t index = buffer.rfind(s);
   //size_t index = buffer.find_last_of(s);
   if (index != std::string::npos) buffer.replace(index, strlen(s), news);
   valid = false;
   return *this;
}
-------------------
> rcpp_string()
replace_all()
AabCDabCDA

replace_first()
AabCDABCDA

replace_last()
AABCDabCDA
-------------------

Regards

Masaki



Masaki Tsuda
teuder at gmail.com

2016/05/17 5:57、Qiang Kou <qkou at umail.iu.edu> のメッセージ:

> Yes, Kevin,
> 
> I think we need something like
> 
> size_t index = std::distance(buffer.begin(), std::search(buffer.begin(), buffer.end(), s.begin(), s.end()));
> 
> KK
> 
>> On Mon, May 16, 2016 at 2:04 PM, Kevin Ushey <kevinushey at gmail.com> wrote:
>> Thanks -- it looks to me like there is something more fundamentally
>> wrong with the 'replace_first' and 'replace_last' methods; ie, I don't
>> think we want to be using 'find_first_of' and 'find_last_of'
>> functions.
>> 
>> Ie, when writing
>> 
>>     string.replace_first("foo", "bar");
>> 
>> I imagine we want to replace the first occurrence of 'foo' with 'bar',
>> and not the first discovered character of 'f' and 'o'.
>> 
>> A simple repro for the bogus behavior:
>> 
>> #include <Rcpp.h>
>> using namespace Rcpp;
>> 
>> // [[Rcpp::export]]
>> String replace() {
>>   String foo("abba");
>>   return foo.replace_first("ba", "BA");
>> }
>> 
>> /*** R
>> replace()
>> */
>> 
>> gives
>> 
>> > replace()
>> [1] "BAba"
>> 
>> which is I doubt what anyone would expect.
>> 
>> On Sun, May 8, 2016 at 6:14 AM, 津田真樹 <teuder at gmail.com> wrote:
>> > I find a bug in String::replace_last().
>> >
>> > I can reproduce the bug with the following code.
>> > (I also showed output of replace_first and replace_all for comparison.)
>> >
>> >
>> > =============
>> > // [[Rcpp::export]]
>> > void rcpp_string(){
>> >
>> >     String s("abcdabcd");
>> >     Rcout << "replace_first()\n";
>> >     Rcout << s.replace_first("ab", "AB").get_cstring() << "\n";
>> >     Rcout << "\n";
>> >
>> >     s="abcdabcd";
>> >     Rcout << "replace_last()\n";
>> >     Rcout << s.replace_last("ab", "AB").get_cstring()  << "\n";
>> >     Rcout << "\n";
>> >
>> >     s="abcdabcd";
>> >     Rcout << "replace_all()\n";
>> >     Rcout << s.replace_all("ab", "AB").get_cstring()  << "\n";
>> >     Rcout << "\n";
>> > }
>> > =============
>> >
>> > output
>> > =============
>> > replace_first()
>> > ABcdabcd
>> >
>> > replace_last()
>> > abcdaABd
>> >
>> > replace_all()
>> > ABcdABcd
>> > =============
>> >
>> >
>> > I also tried to fix the bug with following code. And the bug seems to be fixed.
>> >
>> > =============
>> > inline String& replace_last(const char* s, const char* news) {
>> >     RCPP_STRING_DEBUG_2("String::replace_last(const char* = '%s' , const char* = '%s')", s, news);
>> >     if (is_na()) return *this;
>> >     setBuffer();
>> >     //size_t index = buffer.find_last_of(s);
>> >     size_t index = buffer.find_last_of(s) - (strlen(s)-1);
>> >     Rcout << "A" << index << "\n";
>> >     if (index != std::string::npos) buffer.replace(index, strlen(s), news);
>> >     valid = false;
>> >     return *this;
>> > }
>> > =============
>> >
>> > output
>> > =============
>> > replace_first()
>> > ABcdabcd
>> >
>> > replace_last()
>> > abcdABcd
>> >
>> > replace_all()
>> > ABcdABcd
>> > =============
>> >
>> >
>> > Mac OS 10.10.5
>> > R version 3.2.3
>> > Rcpp 0.12.4
>> >
>> >
>> > _______________________________________________
>> > Rcpp-devel mailing list
>> > Rcpp-devel at lists.r-forge.r-project.org
>> > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
>> _______________________________________________
>> Rcpp-devel mailing list
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> 
> 
> 
> -- 
> Qiang Kou
> qkou at umail.iu.edu
> School of Informatics and Computing, Indiana University
> 
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