Walk lists with for, and take a message's rows

for item in list [where condition] { ... } runs its block in a handler
once for every item the list has, in order, the item an index of the list
(read, changed, removed: a removed item does not skip the next). It
compiles to Pure's EACH; a fold inside reads the walk's item as a fold in
a column reads its row. A for adds nothing to the list it walks, holds no
other for and does not reply, so it ends.

A message field may be a list of a record (lines: list of Line): its rows
arrive as a JSON array of objects and fill a list of their own, named
order.lines in the module, which the handler walks, folds and counts
(order.lines.count) and which is emptied when the event ends. So a
transaction over many rows (an order taking stock line by line, all or
nothing) and a bulk insert are one event. An output sends no rows.

Nine diagnostics and an accepted app (rows in a group, where, a fold over
the rows reading the walk's item, a walk that removes) are checked.

0 files changed, 0 insertions, 0 deletions