Can't Iterate Over List Directly about penlight

[stevedonovan]

Yep, you're right, the docs do say this. But the code was taken out, apologies for the gap.

The reason is simple: the list itself has to keep the state.

-- NOTE: this works, but is unreliable. If you leave the loop before finishing,
-- then the iterator is not reset.
--- can iterate over a list directly.
-- @Usage for v in ls do print(v) end
function List:__call()
if not self.key then self.key = 1 end
local value = self[self.key]
self.key = self.key + 1
if not value then self.key = nil end
return value
end

Now as long as you complete each iteration, cool. If you jump out, then the list is in a particular iteration state. Next time you try to iterate, you get the wrong results.

Which is why I now suggest an explicit iterator: l:iter()

steve d.

[kevincox]

Okay, thank you. Can the doc's be updated?

On Wed, Jan 4, 2012 at 2:11 AM, Steve J Donovan <
[email protected]

wrote:

Yep, you're right, the docs do say this. But the code was taken out,
apologies for the gap.

The reason is simple: the list itself has to keep the state.

-- NOTE: this works, but is unreliable. If you leave the loop before
finishing,
-- then the iterator is not reset.
--- can iterate over a list directly.
-- @Usage for v in ls do print(v) end
function List:__call()
if not self.key then self.key = 1 end
local value = self[self.key]
self.key = self.key + 1
if not value then self.key = nil end
return value
end

Now as long as you complete each iteration, cool. If you jump out, then
the list is in a particular iteration state. Next time you try to iterate,
you get the wrong results.

Which is why I now suggest an explicit iterator: l:iter()

steve d.

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