Maximum number of objects in r workspace

Question

Is there a limit on the number (not size) of objects an R workspace may contain? What is the maximum possible value of length(e), where e is an environment?

(length(e) contains the number of variable in e; it is the same as length(ls(e)).)

Answer 1

The source code for ls() (in src/main/envir.c) defines it's return value using another function: return R_lsInternal(env, all);;

 #2518 SEXP attribute_hidden do_ls(SEXP call, SEXP op, SEXP args, SEXP rho)
 #2519 {
 #2520     SEXP env;
 #2521     int all;
 #....
 #2537     return R_lsInternal(env, all);
 #2538 }

The return function return R_lsInternal(env, all);, takes a list of environments and a boolean indicating whether to get all names and is defined at line 2452 of the envir.c. It computes the length of names of objects in an environment(s) storing the length in an int datatype (k below), therefore the number of objects in an environment must be bounded by the maximum size of this datatype:

 #2542 SEXP R_lsInternal(SEXP env, Rboolean all)
 #2543 {
 #2544     int  k;    <==== INTEGER TYPE DEFINED HERE LIMITS NUMBER OF OBJECTS IN ENVIRONMENT
 #2545     SEXP ans;
 #2546 
 #2547 
 #2548     /* Step 1 : Compute the Vector Size */
 #2549     k = 0;
 #2550     if (env == R_BaseEnv || env == R_BaseNamespace)
 #2551     k += BuiltinSize(all, 0);
 #...
 #2562     /* Step 2 : Allocate and Fill the Result */
 #2563     PROTECT(ans = allocVector(STRSXP, k));
 #...
 #2576     return ans;
 #2577 }

However, this is for the objects in a specified environment. I see no reason that you can't specify sub-environements, each of which could have .Machine$integer.max objects in it! So the limit should only be bounded by your machine memory. I'd love someone to test this though!

#  Example of assigning values in sub environments...
e <- new.env()
e$f <- new.env()

# Environment `e` now has one object in, which is another environment...
length ( ls( e ) )
# [1] 1

e$f$a <- 2

# Environment `f` now also has one object in, which is `a`
length ( ls( e$f ) )
# [1] 1

Note: if you compute the length of objects using length(e) where e is an environment then the function envlength will be dispatched as length is an internal generic for which there are several methods written for various object types, including one for environments, as noted by @RichieCotton above and @hadley in the comments below.