PluggableMemoization

RetryingDelay

->PluggableMemoization

Usage: (->PluggableMemoization f cache)

Positional factory function for class clojure.core.memoize.PluggableMemoization.

->RetryingDelay

Usage: (->RetryingDelay fun available? value)

Positional factory function for class clojure.core.memoize.RetryingDelay.

build-memoizer

Usage: (build-memoizer cache-factory f & args)

Builds a function that, given a function, returns a pluggable memoized
 version of it.  `build-memoizer` takes a cache factory function, and the
 arguments to that factory function -- at least one of those arguments
 should be the function to be memoized (it's usually the first argument).

`memoizer` above is a simpler version of `build-memoizer` that 'does the
right thing' with a cache and a seed hash map. `build-memoizer` remains
for backward compatibility but should be considered deprecated.

fifo

Usage: (fifo f)
       (fifo f base)
       (fifo f tkey threshold)
       (fifo f base key threshold)

Works the same as the basic memoization function (i.e. `memo`
and `core.memoize` except when a given threshold is breached.

Observe the following:

    (require '[clojure.core.memoize :as memo])

    (def id (memo/fifo identity :fifo/threshold 2))

    (id 42)
    (id 43)
    (snapshot id)
    ;=> {[42] 42, [43] 43}

As you see, the limit of `2` has not been breached yet, but
if you call again with another value, then it is:

    (id 44)
    (snapshot id)
    ;=> {[44] 44, [43] 43}

That is, the oldest entry `42` is pushed out of the
memoization cache.  This is the standard **F**irst **I**n
**F**irst **O**ut behavior.

lazy-snapshot

Usage: (lazy-snapshot memoized-fn)

Returns a lazy snapshot of a core.memo-placed memoization cache.  By
lazy snapshot you can infer that what you get is only the cache contents at a
moment in time -- and, being lazy, the cache could change while you are
realizing the snapshot elements.

Returns a sequence of key/value pairs.

lru

Usage: (lru f)
       (lru f base)
       (lru f tkey threshold)
       (lru f base key threshold)

Works the same as the basic memoization function (i.e. `memo`
and `core.memoize` except when a given threshold is breached.

Observe the following:

    (require '[clojure.core.memoize :as memo])

    (def id (memo/lru identity :lru/threshold 2))

    (id 42)
    (id 43)
    (snapshot id)
    ;=> {[42] 42, [43] 43}

At this point the cache has not yet crossed the set threshold
of `2`, but if you execute yet another call the story will
change:

    (id 44)
    (snapshot id)
    ;=> {[44] 44, [43] 43}

At this point the operation of the LRU cache looks exactly
the same at the FIFO cache.  However, the difference becomes
apparent on further use:

    (id 43)
    (id 0)
    (snapshot id)
    ;=> {[0] 0, [43] 43}

As you see, once again calling `id` with the argument `43`
will expose the LRU nature of the underlying cache.  That is,
when the threshold is passed, the cache will expel the
**L**east **R**ecently **U**sed element in favor of the new.

lu

Usage: (lu f)
       (lu f base)
       (lu f tkey threshold)
       (lu f base key threshold)

Similar to the implementation of memo-lru, except that this
function removes all cache values whose usage value is
smallest:

    (require '[clojure.core.memoize :as memo])

    (def id (memo/lu identity :lu/threshold 3))

    (id 42)
    (id 42)
    (id 43)
    (id 44)
    (snapshot id)
    ;=> {[44] 44, [42] 42}

The **L**east **U**sed values are cleared on cache misses.

memo

Usage: (memo f)
       (memo f seed)

Used as a more flexible alternative to Clojure's core `memoization`
function.  Memoized functions built using `memo` will respond to
the core.memo manipulable memoization utilities.  As a nice bonus,
you can use `memo` in place of `memoize` without any additional
changes, with the added guarantee that the memoized function will
only be called once for a given sequence of arguments (`memoize`
can call the function multiple times when concurrent calls are
made with the same sequence of arguments).

The default way to use this function is to simply supply a function
that will be memoized.  Additionally, you may also supply a map
of the form `'{[42] 42, [108] 108}` where keys are a vector
mapping expected argument values to arity positions.  The map values
are the return values of the memoized function.

If the supplied function has metadata containing an
`:clojure.core.memoize/args-fn` key, the value is assumed to be a
function that should be applied to the arguments to produce a
subset or transformed sequence of arguments that are used for the
key in the cache (the full, original arguments will still be used
to call the function). This allows you to memoize functions where
one or more arguments are irrelevant for memoization, such as the
`clojure.java.jdbc` functions, whose first argument may include
a (mutable) JDBC `Connection` object:

  (memo/memo (with-meta jdbc/execute! {::memo/args-fn rest}))

You can access the memoization cache directly via the `:clojure.core.memoize/cache` key
on the memoized function's metadata.  However, it is advised to
use the core.memo primitives instead as implementation details may
change over time.

memo-clear!

Usage: (memo-clear! f)
       (memo-clear! f args)

Reaches into an core.memo-memoized function and clears the cache.  This is a
destructive operation and should be used with care.

When the second argument is a vector of input arguments, clears cache only
for argument vector.

Keep in mind that depending on what other threads or doing, an
immediate call to `snapshot` may not yield an empty cache.  That's
cool though, we've learned to deal with that stuff in Clojure by
now.

memo-fifo

Usage: (memo-fifo f)
       (memo-fifo f limit)
       (memo-fifo f limit base)

DEPRECATED: Please use clojure.core.memoize/fifo instead.

memo-lru

Usage: (memo-lru f)
       (memo-lru f limit)
       (memo-lru f limit base)

DEPRECATED: Please use clojure.core.memoize/lru instead.

memo-lu

Usage: (memo-lu f)
       (memo-lu f limit)
       (memo-lu f limit base)

DEPRECATED: Please use clojure.core.memoize/lu instead.

memo-reset!

Usage: (memo-reset! f base)

Takes a core.memo-populated function and a map and replaces the memoization cache
with the supplied map.  This is potentially some serious voodoo,
since you can effectively change the semantics of a function on the fly.

    (def id (memo identity))
    (memo-swap! id '{[13] :omg})
    (id 13)
    ;=> :omg

With great power comes ... yadda yadda yadda.

memo-swap!

Usage: (memo-swap! f base)
       (memo-swap! f swap-fn args & results)

The 2-arity version takes a core.memo-populated function and a map and
replaces the memoization cache with the supplied map. Use `memo-reset!`
instead for replacing the cache as this 2-arity version of `memo-swap!`
should be considered deprecated.

The 3+-arity version takes a core.memo-populated function and arguments
similar to what you would pass to `clojure.core/swap!` and performs a
`swap!` on the underlying cache. In order to satisfy core.memoize's
world view, the assumption is that you will generally be calling it like:

      (def id (memo identity))
      (memo-swap! id clojure.core.cache/miss [13] :omg)
      (id 13)
      ;=> :omg

You'll nearly always use `clojure.core.cache/miss` for this operation but
you could pass any function that would work on an immutable cache, such
as `evict` or `assoc` etc.

Be aware that `memo-swap!` assumes it can wrap each of the `results` values
in a `delay` so that items conform to `clojure.core.memoize`'s world view.

memo-ttl

Usage: (memo-ttl f)
       (memo-ttl f limit)
       (memo-ttl f limit base)

DEPRECATED: Please use clojure.core.memoize/ttl instead.

memoized?

Usage: (memoized? f)

Returns true if a function has an core.memo-placed cache, false otherwise.

memoizer

Usage: (memoizer f cache)
       (memoizer f cache seed)

Build a pluggable memoized version of a function. Given a function and a
(pluggable memoized) cache, and an optional seed (hash map of arguments to
return values), return a cached version of that function.

If you want to build your own cached function, perhaps with combined caches
or customized caches, this is the preferred way to do so now.

snapshot

Usage: (snapshot memoized-fn)

Returns a snapshot of a core.memo-placed memoization cache.  By snapshot
you can infer that what you get is only the cache contents at a
moment in time.

ttl

Usage: (ttl f)
       (ttl f base)
       (ttl f tkey threshold)
       (ttl f base key threshold)

Unlike many of the other core.memo memoization functions,
`memo-ttl`'s cache policy is time-based rather than algorithmic
or explicit.  When memoizing a function using `memo-ttl` you
should provide a **T**ime **T**o **L**ive parameter in
milliseconds.

    (require '[clojure.core.memoize :as memo])

    (def id (memo/ttl identity :ttl/threshold 5000))

    (id 42)
    (snapshot id)
    ;=> {[42] 42}

    ... wait 5 seconds ...
    (id 43)
    (snapshot id)
    ;=> {[43] 43}

The expired cache entries will be removed on each cache **miss**.