On Tue, Oct 23, 2012 at 2:58 PM, Jim - FooBar(); <[email protected]>wrote:
> On 23/10/12 19:57, Brian Hurt wrote:
>
>> Unless you don't need to do it at all.
>>
>
> niiiice... ;-)
>
>
I was actually serious. One of the advantages of lazy eval is that it lets
you delay deciding whether or not to do a computation until you actually
need the result- if there is a decent chance you won't, then it's a win.
So it lets you play games like:
(let [ lst (map expensive_function (range 1000000000)) ]
; Note, lst is lazily evaluated, the above expression is O(1) cost!
...
; Later- nah, I've changed my mind, I only need the first 10 elements
(take 10 lst)
Note that we haven't paid the cost of evaluating all billion calls to
expensive_function, we've only paid the cost of doing it 10 times- skipping
the remaining 999,999,990 calls.
Brian
>
> Jim
>
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