How can I apply a name to an environment?

Question

The global environment seems to have the name R_GlobalEnv

environment()
# <environment: R_GlobalEnv>

I'd like to attach a name to a new environment e so that if I name it myEnv, it reads

e
# <environment: myEnv>

But it doesn't seem like this is possible. There are no arguments in new.env that allow this, and attr<- doesn't seem to work.

e <- new.env()
attr(e, "names") <- "myEnv"
# Error in attr(e, "names") <- "myEnv" : names() applied to a non-vector

Is it possible to name the environment, maintain the byte code, and have it print as shown above?

Answer 1

From ?environment:

System environments, such as the base, global and empty environments, have names as do the package and namespace environments and those generated by ‘attach()’. Other environments can be named by giving a ‘"name"’ attribute

Therefore:

attr(e, "name") <- "yip"
e
#<environment: 0x00000000080974f8>
#attr(,"name")
#[1] "yip"
environmentName(e)
#[1] "yip"

Answer 2

You can give it a class and write an S3 print method

> e <- new.env()
> class(e) <- "myClass"
> print.myClass <- function(x, ...) cat("<environment: myEnv>\n")
> e
<environment: myEnv>

---

Combining @thelatemail's answer with mine... you could do this

e <- new.env()
print.myClass <- function(x, ...) cat("<environment: ", environmentName(x), ">\n", sep="")
class(e) <- "myClass"
e
#<environment: >
attr(e, "name") <- "myEnv"
e
#<environment: myEnv>

Answer 3

According to the code used to print environments (./src/main/printutils.c as of r66641), you can't get it to print as:

> e
<environment: myEnv>

Here's the relevant section of printutils.c:

attribute_hidden
const char *EncodeEnvironment(SEXP x)
{
    const void *vmax = vmaxget();
    static char ch[1000];
    if (x == R_GlobalEnv)
    sprintf(ch, "<environment: R_GlobalEnv>");
    else if (x == R_BaseEnv)
    sprintf(ch, "<environment: base>");
    else if (x == R_EmptyEnv)
    sprintf(ch, "<environment: R_EmptyEnv>");
    else if (R_IsPackageEnv(x))
    snprintf(ch, 1000, "<environment: %s>",
        translateChar(STRING_ELT(R_PackageEnvName(x), 0)));
    else if (R_IsNamespaceEnv(x))
    snprintf(ch, 1000, "<environment: namespace:%s>",
        translateChar(STRING_ELT(R_NamespaceEnvSpec(x), 0)));
    else snprintf(ch, 1000, "<environment: %p>", (void *)x);

    vmaxset(vmax);
    return ch;
}