https://github.com/eddelbuettel/tidycpp
Tidy C++ wrapping of the C API of R
https://github.com/eddelbuettel/tidycpp
cpp cran r r-package
Last synced: 3 months ago
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Tidy C++ wrapping of the C API of R
- Host: GitHub
- URL: https://github.com/eddelbuettel/tidycpp
- Owner: eddelbuettel
- Created: 2020-08-10T22:11:30.000Z (almost 5 years ago)
- Default Branch: master
- Last Pushed: 2024-11-17T23:27:46.000Z (8 months ago)
- Last Synced: 2025-03-24T08:02:13.600Z (4 months ago)
- Topics: cpp, cran, r, r-package
- Language: C++
- Homepage:
- Size: 124 KB
- Stars: 38
- Watchers: 4
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: ChangeLog
Awesome Lists containing this project
README
## tidyCpp: Tidy C++ wrapping of the C API for R
[](https://github.com/eddelbuettel/tidycpp/actions?query=workflow%3Aci)
[](https://www.gnu.org/licenses/gpl-2.0.html)
[](https://cran.r-project.org/package=tidyCpp)
[](https://cran.r-project.org/package=tidyCpp)
[](https://www.r-pkg.org/pkg/tidyCpp)
[](https://github.com/eddelbuettel/tidycpp)
### About
The C API of the R language and environment is robust, yet a little awkward for C++ programmers.
This package wraps a tidy layer of header functions around it.
R Core is moving towards a more explicit classification of which functions are officially part of
the API for R, and which ones are 'experimental'. A [very helpful contributed
page](https://aitap.codeberg.page/R-api) summarizes the status.
### Examples
A recent motivating example is from the
[dang](https://github.com/eddelbuettel/dang/blob/master/src/checkNonAscii.cpp) package which
includes one unexported Base R function written in C. The original version is
[here](https://github.com/wch/r-source/blob/trunk/src/library/tools/src/text.c#L140-L184). While
short enough, we found working with a _tidier_ version easier and more enjoyable. We include an
abbreviated version (minus the copyright header) here:
```c++
#include
extern "C" {
// cf src/library/tools/src/text.c
SEXP _check_nonASCII(SEXP text, SEXP ignore_quotes) {
/* Check if all the lines in 'text' are ASCII, after removing
comments and ignoring the contents of quotes (unless ignore_quotes)
(which might span more than one line and might be escaped).
This cannot be entirely correct, as quotes and \ might occur as
part of another character in a MBCS: but this does not happen
in UTF-8.
*/
int i, nbslash = 0; /* number of preceding backslashes */
const char *p;
char quote= '\0';
Rboolean ign, inquote = FALSE;
if (!R::isString(text)) R::error("invalid input");
ign = (Rboolean) R::asLogical(ignore_quotes);
if (ign == NA_LOGICAL) R::error("'ignore_quotes' must be TRUE or FALSE");
for (i = 0; i < R::length(text); i++) {
p = R::charPointer(R::stringElement(text, i)); // ASCII or not not affected by charset
inquote = FALSE; /* avoid runaway quotes */
for (; *p; p++) {
if (!inquote && *p == '#') break;
if (!inquote || ign) {
if ((unsigned int) *p > 127) {
Rprintf("%s\n", R::charPointer(R::stringElement(text, i)));
Rprintf("found %x\n", (unsigned int) *p);
return R::scalarLogical(TRUE);
}
}
if ((nbslash % 2 == 0) && (*p == '"' || *p == '\'')) {
if (inquote && *p == quote) {
inquote = FALSE;
} else if(!inquote) {
quote = *p;
inquote = TRUE;
}
}
if (*p == '\\') nbslash++; else nbslash = 0;
}
}
return R::scalarLogical(FALSE);
}
} // extern "C"
```
Additions from the `tidyCpp` wrapper can be identified easily via the `R::` namespace. While the
code is not hiding its C heritage, we find it overall a little easier to work with. Other examples
(see below) show how using `tidyCpp` can help avoid the very manual and error-prone `PROTECT` and
`UNPROTECT` and pairs.
For additional examples, please see the
[Motivation](https://cran.r-project.org/package=tidyCpp/vignettes/motivation.html) vignette for a
longer discussion with more examples, and the files in the
[snippets/](https://github.com/eddelbuettel/tidycpp/tree/master/inst/snippets) directory for
directly callable code examples.
### Author
Dirk Eddelbuettel
### License
GPL (>= 2)