On Sat, May 29, 2010 at 08:52:59PM -0700, ataggart wrote:
> Yup, you need to use the transient functions, e.g., assoc!, just as
> you would the persistent functions. This is nice since you can write
> your code in the persistent style, then if you need to make some
> performance tweaks, simply add some exclamation points; the structure
> of the code remains the same.
>
> As for why you see what you're seeing, the assoc! does generally
> mutate the passed in map, thus you see some map entries. The rub is
> that assoc! is smart enough to choose the right implementation for the
> size; for small maps (0-8 entries) an array-map is used (and the {}
> literal is also an array-map). Once you assoc! the 9th element, the
> function instead returns a hashmap, thus no longer mutating the
> instance referenced by thm.
Ah, yes:
user> (loop [thm (transient {}),
i 0]
(if (<= 10 i)
(persistent! thm)
(recur (assoc! thm i i)
(inc i))))
{0 0, 1 1, 2 2, 3 3, 4 4, 5 5, 6 6, 7 7, 8 8, 9 9}
So, a fundamental misconception of mine then ;)
Thanks!
Daniel
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