How to see source code for functions written in C/C++?

Question

In general, the source code for functions written in R can be looked up just by typing the name of the function on R console. How do you do it for functions which are written in C or C++?

For e.g. when I try and look up the code for lapply() function, it shows me this -

function (X, FUN, ...) 
{
    FUN <- match.fun(FUN)
    if (!is.vector(X) || is.object(X)) 
        X <- as.list(X)
    .Internal(lapply(X, FUN))
}
<bytecode: 0x0000000007384128>
<environment: namespace:base>

which doesn't help in anyways to understand what exactly this function is doing.

C and C++ are both compiled languages, if you have the source from which it was compiled then you can get the definitions, otherwise you are out of luck. — David Rodríguez - dribeas, Aug 21 '13 at 02:46
@JoshuaUlrich My question seems like an exact duplicate of the question linked. Should I delete this question? — steadyfish, Aug 21 '13 at 03:00
I think this question is useful because it rephrases the question linked. So, the answer might be same but rephrasing the question to have C/C++ or lapply is beneficial in my opinion. — kaisernahid, Aug 21 '13 at 07:31

score 2 · Answer 1 · answered Aug 21 '13 at 02:58

2

You can search for lapply or any other function in this mirror of R source repository: https://github.com/wch/r-source

Then choose C/C++ from the languages in the left to get to this page: https://github.com/wch/r-source/search?l=c&q=lapply&ref=cmdform

answered Aug 21 '13 at 02:58

kaisernahid

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13

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You can also Google search the svn repository directly using `site:https://svn.r-project.org/R/` and your desired terms. – thelatemail Aug 21 '13 at 04:12
@thelatemail, yes, but github repository is advantageous over 'site' search in Google as github will allow you to specify C/C++ file too. In our example, there are over 150 R files referring to lapply but only 9 referring to C/C++. – kaisernahid Aug 21 '13 at 07:27
That's easily done with Google by specifying `filetype:c`. – Joshua Ulrich Aug 21 '13 at 10:30

How to see source code for functions written in C/C++?

1 Answers1

Linked