[datatable-help] !J (not-join) just added - please check

[Matthew Dowle]

Hi all,

New feature just added. I had planned to use '-' but realised '!' seems
much better. Running it past you all to double check. If you can see any
problems e.g. backwards compatibility issues, please shout. It doesn't
break any existing tests.

================

A new "!" prefix on i signals not-join (a.k.a. not-select), #1384.
  DT[-DT["a", which=TRUE, nomatch=0]]   # old not-join idiom, still works
  DT[!"a"]                              # same result, now preferred.
  DT[!J(6),...]                         # !J == not-join
  DT[!2:3,...]                          # ! on all types of i
  DT[colA!=6L | colB!=23L,...]          # multiple vector scanning approach
  DT[!J(6L,23L)]                        # same result, faster binary search
'!' has been used rather than '-' :
  * to match the 'not-join' and 'not-select' nomenclature
  * with '-', DT[-0] would return DT rather than DT[0] and not be backwards
    compatibile. With '!', DT[!0] returns DT both before (since !0 is TRUE
    in base R) and after this new feature.
  * to leave DT[+...] and DT[-...] available for future use

================

Links to background in here :

https://r-forge.r-project.org/tracker/index.php?func=detail&aid=1384&group_id=240&atid=978

The new tests are, so far :

DT = data.table(A=rep(1:3,each=2),B=1:6,key="A")
test(788, DT[!J(2)], data.table(A=c(1L,1L,3L,3L),B=c(1L,2L,5L,6L),key="A"))
test(789, DT[!(2:6)], DT[1])
test(790, DT[!(2:6)], DT[!2:6])
test(791, DT[!6], DT[1:5])
test(792, DT[!c(TRUE,FALSE)], DT[c(FALSE,TRUE)])
test(793, setkey(DT[,A:=letters[A]],A)[!c("b","c")], DT["a"])
test(794, DT[!"b"], DT[c("a","c")])
test(795, DT[!0], DT)
test(796, DT[!NULL], DT[NULL])
test(797, DT[!integer()], DT)
test(798, DT[!-1], DT[1])
test(799, DT[--1], DT[1])
myi = c("a","c")
test(800, DT[!myi], DT["b"])
test(801, DT[!"c",sum(B),by=A], data.table(A=c("a","b"),V1=c(3L,7L),key="A"))
test(802, DT[!"missing",sum(B),by=A], DT[,sum(B),by=A])
test(803, DT[!c("a","missing","b","missing2"),sum(B),by=A], DT["c",sum(B)])


Matthew