arrayformula sum in Google spreadsheet

Question

How do you arrayformula() a sum() such as:

=sum(A1:H1)

I need to go down 1000 rows.

Answer 1

Another option:

=ArrayFormula(SUMIF(IF(COLUMN(A1:H1),ROW(A1:A1000)),ROW(A1:A1000),A1:H1000))