Why does the Snake example in the book use refs when all mutation is
done from the EDT?
To verify that, I put a call to "assert-edt" in front of every dosync
in snake.clj. assert-edt is defined like this:
(defn assert-edt [] (assert (javax.swing.SwingUtilities/
isEventDispatchThread)))
And it never throws. So why would I use transactions when Swing is
already taking care of everything? The only reason I see is when you
also want to mutate things for testing in the REPL.
But even in that case, you could still do
(javax.swing.SwingUtilities/invokeAndWait #(mutate-like-crazy))
Second question - in the functional section of snake.clj, there is
this function:
(defn point-to-screen-rect [pt]
(map #(* point-size %)
[(pt 0) (pt 1) 1 1]))
Is it considered functional (=pure?) because point-size is considered
to be constant?
According to the definitions of pure/functional that I've come across
(return value only depends on function parameters, has no side
effects) it would not be pure, as point-size can be changed, affecting
the operation of that function.
But then again in the face of dynamic rebinding (I could even rebind
map to do something completely different), is there anything pure in
clojure at all?
And while I (still) got your attention ;), dynamic rebinding of macros
is impossible because all references to macros disappear in the
compilation phase, correct? Otherwise I could have just rebound dosync
to always call assert-edt first instead of putting it in front of
every "call" to dosync.
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