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- Subject: Re: Dedicated error value/type for Lua?
- From: Rici Lake <lua@...>
- Date: Wed, 22 Dec 2004 00:10:48 -0500
On 21-Dec-04, at 9:04 PM, Mark Hamburg wrote:
The following is a non-ideal example, but the idea is that if one
convention that libraries should return errors rather than throwing
exceptions (see http://lua-users.org/wiki/FinalizedExceptions), then it
would help to have a way to express errors when false and nil are valid
Surely the pcall convention (first result is the success indicator) does
function itemExists( db, itemKey )
-- Returns true if database db contains an item with the
-- given key. Returns false if the database does not contain
-- an item with given key. Returns error in the event of an
-- error reading the database.
Which this example is perfect for:
true, true (or perhaps some more useful value)
true, false -- no such key
false, "Wrong password, bozo" -- database error
exists = error_assert( itemExists( db, itemKey ) )
where error_assert is (in lua 5.1, I think):
function (success, ...)
if success then return ...