R Under development (unstable) (2023-11-16 r85542 ucrt) -- "Unsuffered Consequences"
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> library("R.utils")
Loading required package: R.oo
Loading required package: R.methodsS3
R.methodsS3 v1.8.2 (2022-06-13 22:00:14 UTC) successfully loaded. See ?R.methodsS3 for help.
R.oo v1.25.0 (2022-06-12 02:20:02 UTC) successfully loaded. See ?R.oo for help.

Attaching package: 'R.oo'

The following object is masked from 'package:R.methodsS3':

    throw

The following objects are masked from 'package:methods':

    getClasses, getMethods

The following objects are masked from 'package:base':

    attach, detach, load, save

R.utils v2.12.3 successfully loaded. See ?R.utils for help.

Attaching package: 'R.utils'

The following object is masked from 'package:utils':

    timestamp

The following objects are masked from 'package:base':

    cat, commandArgs, getOption, isOpen, nullfile, parse, warnings

> 
> opager <- options(pager=mpager)
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Example 1
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> cat("=== Example 1 ================================================\n")
=== Example 1 ================================================
> 
> foo <- function(file, ...) {
+   cat("Local objects before calling sourceTo():\n")
+   print(ls())
+ 
+   res <- sourceTo(file, ...)
+ 
+   cat("Local objects after calling sourceTo():\n")
+   print(ls())
+ }
> 
> cat("Global objects before calling foo():\n")
Global objects before calling foo():
> lsBefore <- NA
> lsBefore <- ls()
> foo(file=textConnection(c('a <- 1', 'b <- 2')))
Local objects before calling sourceTo():
[1] "file"
Local objects after calling sourceTo():
[1] "a"    "b"    "file" "res" 
> 
> cat("Global objects after calling foo():\n")
Global objects after calling foo():
> stopifnot(length(setdiff(ls(), lsBefore)) == 0)
> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Example 2 - with VComments preprocessor
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> cat("=== Example 2 ================================================\n")
=== Example 2 ================================================
> 
> preprocessor <- function(lines, ...) {
+   cat("-----------------------------------------\n")
+   cat("Source code before preprocessing:\n")
+   displayCode(code=lines)
+   cat("-----------------------------------------\n")
+   cat("Source code after preprocessing:\n")
+   lines <- VComments$compile(lines)
+   displayCode(code=lines)
+   cat("-----------------------------------------\n")
+   lines
+ }
> 
> oldHooks <- getHook("sourceTo/onPreprocess")
> setHook("sourceTo/onPreprocess", preprocessor, action="replace")
> code <- c(
+  'x <- 2',
+  '#V1# threshold=-1',
+  '#Vc# A v-comment log message',
+  'print("Hello world")'
+ )
> fh <- textConnection(code)
> sourceTo(fh)
-----------------------------------------
Source code before preprocessing:
===============================================================================
R code
===============================================================================

1|x <- 2
2|#V1# threshold=-1
3|#Vc# A v-comment log message
4|print("Hello world")


-----------------------------------------
Source code after preprocessing:
===============================================================================
R code
===============================================================================

1|x <- 2
2|verbose <- Verbose(threshold=-1)
3|if (verbose) { cat(verbose, "A v-comment log message") }
4|print("Hello world")


-----------------------------------------
A v-comment log message
[1] "Hello world"
> setHook("sourceTo/onPreprocess", oldHooks, action="replace")
> 
> options(opager)
> 
> proc.time()
   user  system elapsed 
   0.31    0.07    0.37