[e-lang] Dynamic whenever, composability of Ever* mechanisms

Mark S. Miller markm at caplet.com
Sat Apr 3 12:40:54 EST 2004

At 08:56 AM 4/3/2004  Saturday, Kevin Reid wrote:

>On Apr 2, 2004, at 17:44, Kevin Reid wrote:
>>        whenever.makePairDynamic(inputReporters, thunk{formula()[0]}, interest)
>Oops. This should be:
>        whenever.makePairDynamic(inputReporters, thunk{[formula(), []]}, interest)

Thanks, that makes more sense. Btw, I'm confused about the comment on that 

     * Like whenever/3, but returns a pair of an EverReporter and its
     * EverReactor.
     * <p>
     * Useful if you want to manually subscribe the reactor to a dynamic set of
     * inputs, but never unsubscribe from them, in which case this is more
     * efficient than whenever.dynamic.
    to makePair(inputReporters :EverReporter[],
                formula :near,
                interest :near) :Tuple[EverReporter, EverReactor] {
        whenever.makePairDynamic(inputReporters, thunk{formula()[0]}, interest)

In what way is whenever.makePair/3 more efficient than whenever.dynamic/3, given 
how they are both implemented in terms of whenever.makePairDynamic?

(Here's whenever.dynamic/3:)

     * Like whenever/3, but the formula should return a tuple of the result
     * and additional near EverReporters which the result depends upon.
    to dynamic(inputReporters :EverReporter[],
               pairFormula :near,
               interest :near) :EverReporter {
        whenever.makePairDynamic(inputReporters, pairFormula, interest)[0]

Text by me above is hereby placed in the public domain


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