On Fri, 21 Oct 2016, William Dunlap via R-devel wrote:
Am 21.10.2016 um 18:10 schrieb William Dunlap:
Are you saying that
f1 <- function(x) log(x)
f2 <- function(x) { log } (x)
should act differently?
yes.
But that would mean that {log} would act differently than log.
I suppose it is a matter of taste, but I say yuck.
As for 'return', don't use it if you want readable code. It is
like a goto but worse. It is never necessary.
As a rule I agree, but one case where return is clearer than the alternative is
repeat {
....
if (...)
return(...)
}
Complicated nested if expressions are also sometimes clearer using
return as an early breakout.
Best,
luke
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Fri, Oct 21, 2016 at 10:17 AM, Wilm Schumacher <wilm.schumac...@gmail.com
wrote:
Hi,
Am 21.10.2016 um 18:10 schrieb William Dunlap:
Are you saying that
f1 <- function(x) log(x)
f2 <- function(x) { log } (x)
should act differently?
yes. Or more precisely: I would expect that. "Should" implies, that I want
to change something. I just want to understand the behavior (or file a bug,
if this would have been one).
As I wrote, in e.g. node.js the pendents to the lines that you wrote are
treated differently (the first is a function, the latter is a parsing
error).
Let's use this example instead:
x <- 20
f1 <- function(x) { x<-x+1; log(x) }
f2 <- function(x) { x<-x+1; log } (x)
which act equally.
But as the latter is a legal statement, I would read it as
f2 <- (function(x) { x<-x+1; log }) (x)
thus, I would expect the first to be a function, the latter to be a
numeric ( log(20) in this case ).
Using 'return' complicates the matter, because it affects evaluation, not
parsing.
But perhaps it illustrates my problem a little better:
x <- 20
f1 <- function(x) return(log(x))
f2 <- function(x) { return(log) } (x)
f1(10) is a numeric, f2(10) is the log function. Again: as the latter is a
legal statement, I would expect:
f2 <- (function(x) { x<-x+1; log }) (x)
However, regarding the answers I will try to construct the AST regarding
the grammar defined in gramm.y of that statement
f2 <- function(x) { x<-x+1; log } (x)
to understand what the R interpreter really does.
Best wishes,
Wilm
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Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
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