What is the purpose of the rho environment argument in R? -


as explained here, when internal or primitive function called, last argument rho, environment in call executed.

on other hand, have r_globalcontext->sysparent — environment() returns in r. sysparent field described as

/* evaluation context structure */ typedef struct rcntxt {     ...     sexp sysparent;     /* environment closure called */     ... }

it seems meaning of rho , sysparent same.

thus, questions are:

  1. if same, why bother pass rho argument?
  2. if not same, how/when differ?
  3. if inside .call function, how hold of rho call internal r functions, short of passing r wrapper?


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