[datatable-help] Error on := causes data.table to be left in a bad state

[Matthew Dowle]

Agreed. That doesn't seem to be precisely what you really had at the
prompt (notice the 10 vs 100) but a good find, yes, please raise.

> 99% positive this is a bug but I like to get confirmation before
> making reports.  Still on 2.12.1 64-bit R on Linux, latest SVN version
> of data.table with debugging turned on.
>
> If you do
>
> DT <- data.table(x=1:10)
>
> DT[, a := letters]
>
>
> You will get the error:
>
> Error in `[.data.table`(DT, , `:=`(a, letters)) :
>   Tried to assign 26 items to target of 100 (can recycle but must be
> exact multiple). If users ask us to change this to a warning, we will
> change it; please ask maintainer('data.table').
>
>
> Which is fine.  However, the state of DT after that is that DT has two
> columns, x (the column it started with) and a, a column full of NULL
> values. If I then try to do something like
>
> DT[, a:=5]
>
> It will say the following error:
>
> Error in `[.data.table`(DT, , `:=`(a, 5)) :
>   cannot coerce type 'double' to vector of type 'NULL'
>
>
> Finally, if I make DT bigger, and try the same thing:
>
> DT <- data.table(x=1:1e6)
> DT[, a := letters]
>
> It will give me the same error message, but now the state of DT is
> even more screwed up. If I try to just print DT I get:
>
>> DT
> Error in names(ans) = names(x) :
>   'names' attribute [2] must be the same length as the vector [1]
> _______________________________________________
> datatable-help mailing list
> datatable-help at lists.r-forge.r-project.org
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
>