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

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
– David Rodríguez - dribeas, Commented Aug 21, 2013 at 2:46
@JoshuaUlrich My question seems like an exact duplicate of the question linked. Should I delete this question? — steadyfish
– steadyfish, Commented Aug 21, 2013 at 3:00
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
– kaisernahid, Commented Aug 21, 2013 at 7:31

kaisernahid · Accepted Answer · 2013-08-21 02:58:26Z

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, 2013 at 2:58

kaisernahid

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3 Comments

thelatemail Over a year ago

You can also Google search the svn repository directly using site:https://svn.r-project.org/R/ and your desired terms.

kaisernahid Over a year ago

@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++.

Joshua Ulrich Over a year ago

That's easily done with Google by specifying filetype:c.

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