Here is a patch to function 'stopifnot' that adds 'evaluated' argument and
makes 'exprs' argument in 'stopifnot' like 'exprs' argument in 'withAutoprint'.
--- stop.R 2019-05-30 14:01:15.282197286 +0000
+++ stop_new.R 2019-05-30 14:01:51.372187466 +0000
@@ -31,7 +31,7 @@
.Internal(stop(call., .makeMessage(..., domain = domain)))
}
-stopifnot <- function(..., exprs, local = TRUE)
+stopifnot <- function(..., exprs, evaluated = FALSE, local = TRUE)
{
n <- ...length()
if(!missing(exprs)) {
@@ -41,21 +41,19 @@
else if(isFALSE(local)) .GlobalEnv
else if (is.environment(local)) local
else stop("'local' must be TRUE, FALSE or an environment")
- exprs <- substitute(exprs) # protect from evaluation
- E1 <- if(is.call(exprs)) exprs[[1]]
+ E1 <- if(!evaluated && is.call(exprs <- substitute(exprs))) exprs[[1]]
cl <- if(is.symbol(E1) &&
- (E1 == quote(`{`) || E1 == quote(expression))) {
+ E1 == quote(`{`)) {
exprs[[1]] <- quote(stopifnot) ## --> stopifnot(*, *, ..., *)
:
exprs
}
else
as.call(c(quote(stopifnot),
- if(is.null(E1) && is.symbol(exprs) &&
- is.expression(E1 <- eval(exprs))) # the *name*
of an expression
- as.list(E1)
+ if(is.expression(exprs))
+ exprs
else
as.expression(exprs)
- )) # or fail ..
+ ))
names(cl) <- NULL
return(eval(cl, envir=envir))
}
--------------------------------------------
Subject: Re: [Rd] stopifnot
To: "Martin Maechler" <maech...@stat.math.ethz.ch>
Cc: r-devel@r-project.org
Date: Monday, 15 April, 2019, 2:56 AM
Also, in current definition of function 'stopifnot' in R 3.6.0 beta or R devel,
for 'cl' if 'exprs' is specified, there a case with comment "the *name* of an
expression". The intent is allowing
stopifnot(exprs = ee) ,
where variable 'ee' holds an expression object, to work on the expression
object.
It is not quite right to use eval(exprs) . It fails when 'stopifnot' is called
inside a function, like
f <- function(ee) stopifnot(exprs = ee)
f(expression())
But, how about local=FALSE case? Should the following work?
f <- function(ee) stopifnot(exprs = ee, local = FALSE)
f(expression())
But, why bother making it work, while it is undocumented that 'exprs' argument
in 'stopifnot' can be an expression? Well, yes, expectation may be set from the
name "exprs" itself or from argument 'exprs' in function 'source' or
'withAutoprint'. Function 'withAutoprint' may be the closest match.
Function 'withAutoprint' has 'evaluated' argument that controls whether work is
on value of 'exprs' or on 'exprs' as given. I like the approach.
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