I've enclosed a modified definition of update-in that allows the
update function "f" to take arguments in addition to "old" value being
updated. The new definition does everything the old definition does
(when additional arguments are not supplied), but it allows "f" to be
an existing function more of the time rather than a new closure that
packages up additional arguments.
Here's an example:
user=> (def m {:a {:b 1}})
#=(var user/m)
user=> (update-in m [:a :b] inc)
{:a {:b 2}}
user=> (update-in m [:a :b] #(+ % 2)) ; current or new
{:a {:b 3}}
user=> (update-in m [:a :b] + 2) ; new
{:a {:b 3}}
Suggested update-in:
(defn update-in
"'Updates' a value in a nested associative structure, where ks is a
sequence of keys and f is a function that will take the old value
and any
supplied args and return the new value, and returns a new nested
structure. If any levels do not exist, hash-maps will be created."
([m [k & ks] f & args]
(if ks
(assoc m k (apply update-in (get m k) ks f args))
(assoc m k (apply f (get m k) args)))))
--Steve
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