Re: [Rd] creating environments in package's C code

[Duncan Murdoch]

On 10/1/2009 12:37 PM, Jeff Horner wrote:
Jeff Horner wrote:
Martin Becker wrote:
Dear developers,
is it possible to create environments in C code of packages?
Simply using
 SEXP env;
 PROTECT (env  = allocSExp(ENVSXP));
and assigning the enclosing environment with SET_ENCLOS seems to be 
insufficient.

Best wishes,

Here's a function I use in rapache to create one:

static SEXP NewEnv(SEXP enclos){
    SEXP env;
    PROTECT(env = allocSExp(ENVSXP));

    SET_FRAME(env, R_NilValue);
    SET_ENCLOS(env, (enclos)? enclos: R_GlobalEnv);
    SET_HASHTAB(env, R_NilValue);
    SET_ATTRIB(env, R_NilValue);

    UNPROTECT(1);

    return env;
}

Oops! I forgot the definition of my simple function NewInteger:

static SEXP NewInteger(int i){
     SEXP val;
     PROTECT(val = NEW_INTEGER(1));
     INTEGER_DATA(val)[0] = i;
     UNPROTECT(1);
     return val;
}



and an example that creates a new environment and then assigns a 
variable named OK an integer vector length 1 with value 0:

SEXP env = NewEnv(R_GlobalEnv);
defineVar(install("OK"),NewInteger(0),env);


One comment:  I would protect the env, because install() and 
NewInteger() could each trigger a garbage collection.  That is, use

SEXP env;
PROTECT(env = NewEnv(R_GlobalEnv));
defineVar(install("OK"),NewInteger(0),env);
UNPROTECT(1);

Duncan Murdoch

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