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Issues with pointers and reference in Rcpp

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0

$begingroup$

I have taken the below code from an exerpt from the wikipedia page on Hilbert curves.

#include <Rcpp.h>
using namespace Rcpp;

//rotate/flip a quadrant appropriately
// [[Rcpp::export]]
void rot(int n, int *x, int *y, int rx, int ry) 
 if (ry == 0) 
 if (rx == 1) 
 *x = n-1 - *x;
 *y = n-1 - *y;
 

 //Swap x and y
 int t = *x;
 *x = *y;
 *y = t;
 


//convert (x,y) to d
// [[Rcpp::export]]
int xy2d (int n, int x, int y) 
 int rx, ry, s, d=0;
 for (s=n/2; s>0; s/=2) 
 rx = (x & s) > 0;
 ry = (y & s) > 0;
 d += s * s * ((3 * rx) ^ ry);
 rot(s, &x, &y, rx, ry);
 
 return d;


//convert d to (x,y)
// [[Rcpp::export]]
void d2xy(int n, int d, int *x, int *y) 
 int rx, ry, s, t=d;
 *x = *y = 0;
 for (s=1; s<n; s*=2) 
 rx = 1 & (t/2);
 ry = 1 & (t ^ rx);
 rot(s, x, y, rx, ry);
 *x += s * rx;
 *y += s * ry;
 t /= 4;
 



// You can include R code blocks in C++ files processed with sourceCpp
// (useful for testing and development). The R code will be automatically 
// run after the compilation.
//

/*** R
xy2d(5, 27, 33)
*/

The issue is that R does not seem to understand the pointer types.

When I remove all * and & symbols, R successfully sources the file using sourceCpp(), however by removing them I lose the desired pointer/reference behavior, which I was hoping to maintain for performance reasons.

Is anyone with more experience with the Rcpp package familiar with a solution to this issue?

c++ pointers reference rcpp

share|improve this question

asked 17 mins ago

LewkrrLewkrr

11

New contributor

Lewkrr is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  This site is intended for fully functioning code, so I'm not sure if your question is on-topic.
  $endgroup$
  – Juho
  16 mins ago
  

  
  
  
  

add a comment | 

0

$begingroup$

I have taken the below code from an exerpt from the wikipedia page on Hilbert curves.

#include <Rcpp.h>
using namespace Rcpp;

//rotate/flip a quadrant appropriately
// [[Rcpp::export]]
void rot(int n, int *x, int *y, int rx, int ry) 
 if (ry == 0) 
 if (rx == 1) 
 *x = n-1 - *x;
 *y = n-1 - *y;
 

 //Swap x and y
 int t = *x;
 *x = *y;
 *y = t;
 


//convert (x,y) to d
// [[Rcpp::export]]
int xy2d (int n, int x, int y) 
 int rx, ry, s, d=0;
 for (s=n/2; s>0; s/=2) 
 rx = (x & s) > 0;
 ry = (y & s) > 0;
 d += s * s * ((3 * rx) ^ ry);
 rot(s, &x, &y, rx, ry);
 
 return d;


//convert d to (x,y)
// [[Rcpp::export]]
void d2xy(int n, int d, int *x, int *y) 
 int rx, ry, s, t=d;
 *x = *y = 0;
 for (s=1; s<n; s*=2) 
 rx = 1 & (t/2);
 ry = 1 & (t ^ rx);
 rot(s, x, y, rx, ry);
 *x += s * rx;
 *y += s * ry;
 t /= 4;
 



// You can include R code blocks in C++ files processed with sourceCpp
// (useful for testing and development). The R code will be automatically 
// run after the compilation.
//

/*** R
xy2d(5, 27, 33)
*/

The issue is that R does not seem to understand the pointer types.

When I remove all * and & symbols, R successfully sources the file using sourceCpp(), however by removing them I lose the desired pointer/reference behavior, which I was hoping to maintain for performance reasons.

Is anyone with more experience with the Rcpp package familiar with a solution to this issue?

c++ pointers reference rcpp

share|improve this question

asked 17 mins ago

LewkrrLewkrr

11

New contributor

Lewkrr is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  This site is intended for fully functioning code, so I'm not sure if your question is on-topic.
  $endgroup$
  – Juho
  16 mins ago
  

  
  
  
  

add a comment | 

$begingroup$

I have taken the below code from an exerpt from the wikipedia page on Hilbert curves.

#include <Rcpp.h>
using namespace Rcpp;

//rotate/flip a quadrant appropriately
// [[Rcpp::export]]
void rot(int n, int *x, int *y, int rx, int ry) 
 if (ry == 0) 
 if (rx == 1) 
 *x = n-1 - *x;
 *y = n-1 - *y;
 

 //Swap x and y
 int t = *x;
 *x = *y;
 *y = t;
 


//convert (x,y) to d
// [[Rcpp::export]]
int xy2d (int n, int x, int y) 
 int rx, ry, s, d=0;
 for (s=n/2; s>0; s/=2) 
 rx = (x & s) > 0;
 ry = (y & s) > 0;
 d += s * s * ((3 * rx) ^ ry);
 rot(s, &x, &y, rx, ry);
 
 return d;


//convert d to (x,y)
// [[Rcpp::export]]
void d2xy(int n, int d, int *x, int *y) 
 int rx, ry, s, t=d;
 *x = *y = 0;
 for (s=1; s<n; s*=2) 
 rx = 1 & (t/2);
 ry = 1 & (t ^ rx);
 rot(s, x, y, rx, ry);
 *x += s * rx;
 *y += s * ry;
 t /= 4;
 



// You can include R code blocks in C++ files processed with sourceCpp
// (useful for testing and development). The R code will be automatically 
// run after the compilation.
//

/*** R
xy2d(5, 27, 33)
*/

The issue is that R does not seem to understand the pointer types.

When I remove all * and & symbols, R successfully sources the file using sourceCpp(), however by removing them I lose the desired pointer/reference behavior, which I was hoping to maintain for performance reasons.

Is anyone with more experience with the Rcpp package familiar with a solution to this issue?

c++ pointers reference rcpp

share|improve this question

asked 17 mins ago

LewkrrLewkrr

11

New contributor

Lewkrr is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

#include <Rcpp.h>
using namespace Rcpp;

//rotate/flip a quadrant appropriately
// [[Rcpp::export]]
void rot(int n, int *x, int *y, int rx, int ry) 
 if (ry == 0) 
 if (rx == 1) 
 *x = n-1 - *x;
 *y = n-1 - *y;
 

 //Swap x and y
 int t = *x;
 *x = *y;
 *y = t;
 


//convert (x,y) to d
// [[Rcpp::export]]
int xy2d (int n, int x, int y) 
 int rx, ry, s, d=0;
 for (s=n/2; s>0; s/=2) 
 rx = (x & s) > 0;
 ry = (y & s) > 0;
 d += s * s * ((3 * rx) ^ ry);
 rot(s, &x, &y, rx, ry);
 
 return d;


//convert d to (x,y)
// [[Rcpp::export]]
void d2xy(int n, int d, int *x, int *y) 
 int rx, ry, s, t=d;
 *x = *y = 0;
 for (s=1; s<n; s*=2) 
 rx = 1 & (t/2);
 ry = 1 & (t ^ rx);
 rot(s, x, y, rx, ry);
 *x += s * rx;
 *y += s * ry;
 t /= 4;
 



// You can include R code blocks in C++ files processed with sourceCpp
// (useful for testing and development). The R code will be automatically 
// run after the compilation.
//

/*** R
xy2d(5, 27, 33)
*/

share|improve this question

asked 17 mins ago

LewkrrLewkrr

11

New contributor

Lewkrr is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

asked 17 mins ago

LewkrrLewkrr

11

New contributor

Lewkrr is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 17 mins ago

LewkrrLewkrr

11

New contributor

Lewkrr is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 17 mins ago

LewkrrLewkrr

11