R Under development (unstable) (2025-04-19 r88162 ucrt) -- "Unsuffered Consequences"
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> NAME <- "subset"
> source(file.path('_helper', 'init.R'))
> 
> A <- B <- letters[1:5]
> B[2] <- "B"
> B[6] <- "F"
> 
> # - subset ---------------------------------------------------------------------
> 
> local({
+   old.opt <- options(diffobj.style=StyleRaw())
+   on.exit(options(old.opt))
+   a0 <- all.equal(
+     c(as.character(diffChr(A, B)[1:3])),
+     c("< A          > B        ", "@@ 1,5 @@    @@ 1,6 @@  ", "  a            a        ")
+ 
+   )
+   a <- all.equal(
+     c(as.character(diffChr(A, B)[1])), c(as.character(head(diffChr(A, B), 1)))
+   )
+   b <- all.equal(
+     c(as.character(diffChr(A, B)[7:8])), c(as.character(tail(diffChr(A, B), 2)))
+   )
+   c(a0, a, b)
+ })
[1] TRUE TRUE TRUE
> # - subset errors --------------------------------------------------------------
> 
> diff <- diffChr(A, B)
> try(diff[NA_real_]) # "contain NAs or both positive"
Error in .local(x, i, ...) : 
  `i` may not contain NAs or both positive and negative indices
> try(diff[c(-1, 1)]) # "contain NAs or both positive"
Error in .local(x, i, ...) : 
  `i` may not contain NAs or both positive and negative indices
> try(head(diff, 1, 2)) # "does not support arguments"
Error in .local(x, ...) : 
  This method does not support arguments other than `x` or `n`
> try(head(diff, NA)) # "must be integer"
Error in .local(x, ...) : `n` must be integer(1L) and not NA
> try(head(diff, 1:3)) # "must be integer"
Error in .local(x, ...) : `n` must be integer(1L) and not NA
> try(tail(diff, 1:3)) # "must be integer"
Error in .local(x, ...) : `n` must be integer(1L) and not NA
> try(tail(diff, 1, 2)) # "does not support arguments"
Error in .local(x, ...) : 
  This method does not support arguments other than `x` or `n`
> 
> 
> 
> proc.time()
   user  system elapsed 
   0.82    0.09    0.89