I'm always interested in the stuff Zach Tellman does, though I don't always
understand it. I'm curious about this bit:
(memoize (fn [_#] (gensym "node"))
How is that different than
(gensym "node")
I only see with-gensyms called once, so I assume the goal is to have
dynamic bindings set up for that block of code.
(defmacro ^:private with-gensyms
"Makes sure the mapping of node and clusters onto identifiers is
consistent within its scope."
[& body]
`(binding [*node->id* (or *node->id* (memoize (fn [_#] (gensym "node"))))
*cluster->id* (or *cluster->id* (memoize (fn [_#] (gensym
"cluster"))))]
~@body))
https://github.com/ztellman/rhizome/blob/1bca773540a0bd244650293d76374b7f0472025e/src/rhizome/dot.clj
The "or" should ensure that the function is only called once, so why is the
memoize needed? When would the function be called a second time, at which
point the memoized response could be returned?
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