Re: filter an array in place

[Mark Hamburg <mark@...>]

-- Remove items from arr for which fn returns false.
-- If fn throws an exception, the array will get messed up.

function filter_array( arr, fn )

	local n = #arr

	local j = 0 -- insert location

	-- make a pass over the array sliding down the values
	-- that pass the test

	for i = 1, n do
		local v = arr[ i ]
		if fn( v ) then
			j = j + 1
			if j ~= i then
				arr[ j ] = v
			end
		end
	end

	-- clear any trailing entries

	for i = j + 1, n do
		arr[ i ] = nil
	end

end