frame_position
Find the position or distance of a frame on the evaluation stack
Description
The frame position on the stack can be computed by counting frames from the global frame (the bottom of the stack, the default) or from the current frame (the top of the stack).
Usage
frame_position(frame, from = c("global", "current"))Arguments
frame |
The environment of a frame. Can be any object with a
|
from |
Whether to compute distance from the global frame (the bottom of the evaluation stack), or from the current frame (the top of the evaluation stack). |
Details
While this function returns the position of the frame on the evaluation stack, it can safely be called with intervening frames as those will be discarded.
Life cycle
These functions are deprecated and replaced by trace_back().
Examples
fn <- function() g(environment()) g <- function(env) frame_position(env) # frame_position() returns the position of the frame on the evaluation stack: fn() identity(identity(fn())) # Note that it trims off intervening calls before counting so you # can safely nest it within other calls: g <- function(env) identity(identity(frame_position(env))) fn() # You can also ask for the position from the current frame rather # than the global frame: fn <- function() g(environment()) g <- function(env) h(env) h <- function(env) frame_position(env, from = "current") fn()