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: 12 days 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 (about 4 years ago)
• Default Branch: master
• Last Pushed: 2024-10-01T12:41:17.000Z (about 1 month ago)
• Last Synced: 2024-10-12T21:26:16.482Z (26 days ago)
• Topics: cpp, cran, r, r-package
• Language: C++
• Homepage:
• Size: 123 KB
• Stars: 39
• Watchers: 5
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: ChangeLog

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README

        

## tidyCpp: Tidy C++ wrapping of the C API for R

[![CI](https://github.com/eddelbuettel/tidycpp/workflows/ci/badge.svg)](https://github.com/eddelbuettel/tidycpp/actions?query=workflow%3Aci)

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[![CRAN](https://www.r-pkg.org/badges/version/tidyCpp)](https://cran.r-project.org/package=tidyCpp)

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[![Downloads](https://cranlogs.r-pkg.org/badges/tidyCpp?color=brightgreen)](https://www.r-pkg.org/pkg/tidyCpp)

[![Last Commit](https://img.shields.io/github/last-commit/eddelbuettel/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)