New idcol= argument to cbindlist

[MichaelChirico]

2- I suggest adding one more argument to cbindlist, in the spirit of idcol arguement in rbindlist, that prefixes the output column names with the names of the source data when the list of data being joined is named. See below.

l = list(x=data.table(a=1,b=2), y=data.table(a=10,b=20))

$x
       a     b
   <num> <num>
1:     1     2

$y
       d     b
   <num> <num>
1:    10    20

# current/default behavior

cbindlist(l)

       a     b     d     b
   <num> <num> <num> <num>
1:     1     2    10    20

# feature request behavior

cbindlist(l, prefix=TRUE)

     x.a   x.b   y.d   y.b
   <num> <num> <num> <num>
1:     1     2    10    20

Originally posted by @Kamgang-B in #4370 (comment)