borkdude

;; deps.edn:

;; {
;;  :deps {
;;         clj-kondo/clj-kondo {:mvn/version "2021.10.19"}
;;         org.clojars.quoll/asami {:mvn/version "2.2.3"}
;;         }
;;  }

kendfrey

import tactic

def transform : ℚ × ℚ × ℚ × ℚ × ℚ × ℚ × ℚ × ℚ × ℚ → ℚ × ℚ → ℚ × ℚ
| (a, b, c, d, e, f, g, h, i) (x, y) := ((a * x + b * y + c) / (g * x + h * y + i), (d * x + e * y + f) / (g * x + h * y + i))

def xy : ℚ × ℚ := (1, 1)
def xy' : ℚ × ℚ := (1, -1)
def x'y' : ℚ × ℚ := (-1, -1)
def x'y : ℚ × ℚ := (-1, 1)

pesterhazy

This gist lists challenges you run into when building offline-first applications based on IndexedDB, including open-source libraries like Firebase, pouchdb and AWS amplify (more).

Note that some of the following issues affect only Safari. Out of the major browsers, Chrome's IndexedDB implementation is the best.

Backing file on disk (WAL file) keeps growing (Safari)

When this bug occurs, every time you use the indexeddb, the WAL file grows. Garbage collection doesn't seem to be working, so after a while, you end up with gigabytes of data.

Random exceptions when working with a large number of indexeddb databases (Safari)

seancorfield

NOTE: Clojure 1.11 Alpha 2 added update-keys and update-vals which provide similar functionality directly in clojure.core, but with the hash map first and the function second.

Running this code:

clj -Sdeps '{:deps 
             {seancorfield/map-utils 
              {:git/url "https://gist.github.com/seancorfield/6e8dd10799e9cc7527da5510c739e52f"
               :sha "cfde3c2c83379e93ab1a49752611ae663008129f"}}}'

That starts a REPL:

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

athos

(import '[clojure.asm Opcodes Type ClassWriter]
        '[clojure.asm.commons Method GeneratorAdapter])

(defn make-class [name]
  (let [cw (ClassWriter. ClassWriter/COMPUTE_FRAMES)
        init (Method/getMethod "void <init>()")
        meth (Method/getMethod "int fact(int)")]
    (.visit cw Opcodes/V1_6 Opcodes/ACC_PUBLIC (.replace name \. \/) nil "java/lang/Object" nil)
    (doto (GeneratorAdapter. Opcodes/ACC_PUBLIC init nil nil cw)
      (.visitCode)