How to get the C/C++ source code of the a secondary function of R?

Question

I was wondering what is the correct way to get the C/C++ source code of any secondary(to distinguish from the Primitive/Internal ones) function in R. Related questions are here, here, here and here:

Mine is different so that I used "secondary" in my question. For example, the read.table() function, within R console I got:

>?read.table

read.table                package:utils                R Documentation

Data Input

Description:

     Reads a file in table format and creates a data frame from it,
     with cases corresponding to lines and variables to fields in the
     file.

Usage:
     read.table(file, header = FALSE, sep = "", quote = "\"'",
        ......

Or

> getAnywhere(read.table)
A single object matching ‘read.table’ was found
It was found in the following places
  package:utils
  namespace:utils
with value

function (file, header = FALSE, sep = "", quote = "\"'", dec = ".", 

     ......

    attr(data, "row.names") <- row.names
    data
}
<bytecode: 0x560ff88edd40>
<environment: namespace:utils>

Search the website I got:

https://svn.r-project.org/R/trunk/src/library/utils/src/utils.c

https://svn.r-project.org/R/trunk/src/library/utils/src/utils.h

How to get the C/C++ source code of the read.table function instead of R code, if this is reasonable?

Does it have c/c++ code? I see nothing of it in https://svn.r-project.org/R/trunk/src/main/names.c — Anonymous coward, Sep 27 '18 at 21:58
This is another clue I should have. I was not aware that names.c can provide some information. Thanks! — Yifangt, Sep 28 '18 at 17:14

score 5 · Accepted Answer · answered Sep 28 '18 at 05:01

5

The searchable R source code at https://github.com/wch/r-source is really useful for this:

First we can look for the read.table definition

The actual data reading is done by the scan function which in the end uses

.Internal(scan(file, what, nmax, sep, dec, quote, skip, nlines,
[...]

Now scan is mapped to do_scan

So here you are: The underlying C implementation for read.table can be found in src/main/scan.c, starting with the function do_scan.

answered Sep 28 '18 at 05:01

Ralf Stubner

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Thanks Ralf! Your answer is exactly what I was looking for and can't be more clear. – Yifangt Sep 28 '18 at 16:17
@Yifangt You are welcome. Feel free to up-vote/accept the answer. – Ralf Stubner Sep 28 '18 at 16:52

How to get the C/C++ source code of the a secondary function of R?

1 Answers1