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

> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # A symbol
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> x <- 1L
> y <- 2L
> symb <- as.symbol("x")
> print(symb)
x
> expr <- egsub("x", "y", symb, value=FALSE)
> print(expr)
y
> 
> expr2 <- egsub("x", "y", symb, value=TRUE)
> print(expr2)
[1] 2
> 
> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Missing expression
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> expr <- expression(x[,1])
> print(expr)
expression(x[, 1])
> expr2 <- egsub("foo", "bar", expr)
> print(expr2)
expression(x[, 1])
> stopifnot(identical(expr2, expr))
> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # NULLs in expression
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # An expression containing a function definition for a
> # function without arguments.
> expr <- substitute(y <- function() 0)
> print(expr)
y <- function() 0
> # Don't replace anything
> expr2 <- egsub("x", "x", expr)
> print(expr2)
y <- function() 0
> stopifnot(identical(expr2, expr))
> 
> proc.time()
   user  system elapsed 
   0.34    0.12    0.40