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

> 
> x <- 1:10
> y <- seqToIntervals(x)
> print(y)  # [1 10]
     from to
[1,]    1 10
> 
> x <- c(1:10, 15:18, 20)
> y <- seqToIntervals(x)
> print(y)  # [1 10; 15 18; 20 20]
     from to
[1,]    1 10
[2,]   15 18
[3,]   20 20
> 
> z <- intervalsToSeq(y)
> print(z)
 [1]  1  2  3  4  5  6  7  8  9 10 15 16 17 18 20
> stopifnot(all.equal(x,z))
> 
> y <- matrix(c(5,11, 1,10), ncol=2L, byrow=TRUE)
> z <- intervalsToSeq(y, unique=FALSE)
> print(z)
 [1]  5  6  7  8  9 10 11  1  2  3  4  5  6  7  8  9 10
> z <- intervalsToSeq(y, unique=TRUE)
> print(z)
 [1]  5  6  7  8  9 10 11  1  2  3  4
> z <- intervalsToSeq(y, sort=TRUE)
> print(z)
 [1]  1  2  3  4  5  5  6  6  7  7  8  8  9  9 10 10 11
> z <- intervalsToSeq(y, unique=TRUE, sort=TRUE)
> print(z)
 [1]  1  2  3  4  5  6  7  8  9 10 11
> 
> ## Corner cases
> x <- integer(0)
> y <- seqToIntervals(x)
> print(y)
     from to
> str(y)
 int[0 , 1:2] 
 - attr(*, "dimnames")=List of 2
  ..$ : NULL
  ..$ : chr [1:2] "from" "to"
> stopifnot(all.equal(dim(y), c(0,2)))
> 
> proc.time()
   user  system elapsed 
   0.26    0.10    0.35