clj-commons/primitive-math

for the discerning arithmetician

About

Clojure's numeric tower is useful, but it can put a lot of steps between you and simple arithmetic. Unfortunately, while Clojure will warn you when reflection is required to invoke a function, it will not warn you when reflection is required to perform math. The only reliable way to discover whether you're calling clojure.lang.Number.add(Object, Object) or clojure.lang.Number.add(long, long) is to use a profiler or decompiler.

Or, you can just bypass Clojure's math operators altogether.

In the clj-commons.primitive-math namespace, there are equivalents for every arithmetic operator and comparator that will give a reflection warning if it cannot compile down to a simple, predictable, unboxed mathematical operation.

clj-commons.primitive-math> (set! *warn-on-reflection* true)
true
clj-commons.primitive-math> (+ 3 3)
6
clj-commons.primitive-math> (defn adder [x] (+ 1 x))
;; gives a reflection warning
clj-commons.primitive-math> (defn adder [^long x] (+ 1 x))
;; no reflection warning
clj-commons.primitive-math> (+ 3.0 3)
;; gives a reflection warning AND throws an exception

To support operations on both long and double types without any reflection, these operators are defined as macros. This means they cannot be used as higher-order functions:

clj-commons.primitive-math> (apply + [1 2 3])
;; throws a 'cannot take value of macro' exception

In practice, it's usually preferable to import the namespace with a prefix, and use p/+ and p/== operators alongside the normal Clojure functions. However, if in a particular namespace you never need to use higher-order operators, you can call (primitive-math/use-primitive-operators) to swap out the Clojure operators for their primitive equivalents. This can be reversed, using (primitive-math/unuse-primitive-operators).

Notes

Pre-1.0.0 versions of primitive-math used a single-segment namespace. This causes problems for Graal and clj-easy. For 1.0.0, everything was copied under the clj-commons namespace. The code is effectively identical, however, so unless you are using Graal, you don't need to make any changes. If you are using Graal, make sure you only require the clj-commons.* namespaces to avoid issues.

Usage

;;; Lein
[org.clj-commons/primitive-math "1.0.1"]

;;; deps.edn
org.clj-commons/primitive-math {:mvn/version "1.0.1"}

An exhaustive list of operators

+
-
*
/  ;; aliased as 'div'
inc
dec
rem
==
not==
zero?
<=
>=
<
>
min
max
bool-and
bool-or
bool-not
bool-xor
true?
false?
bit-and
bit-or
bit-xor
bit-not
bit-shift-left   ;; aliased as '<<'
bit-shift-right  ;; aliased as '>>'
unsigned-bit-shift-right  ;; aliased as '>>>'
byte
short
int
float
long
double
byte->ubyte
ubyte->byte
short->ushort
ushort->short
int->uint
uint->int
long->ulong
ulong->long
reverse-short
reverse-int
reverse-long

Full documentation can be found at cljdoc.

License

Copyright © 2016 Zachary Tellman

Distributed under the MIT License.