pbostrom

;; with-redefs
``` clojure
(defn print-it []
  (println "don't print this"))

(defn dont-print [x]
  (with-redefs [print-it (constantly nil)]
    (print-it)))

(defn -main []

pbostrom

That’s a lot to take in! No wonder we got it wrong! We’ll take it slow, and look at the arguments.

(condp (* temp time) <

Our pred was (* temp time) (a Double), and our expr was the comparison function <. For each clause, (pred test-expr expr) is evaluated, so that would expand to something like

((* temp time) 400 < )

pbostrom

;; Don't unroll optional named arguments. 
;; While it's nice for callers to not have to wrap optional named arguments in a map, 
;; clearly specified configuration maps are laudable.
(release-sharks 2 :laser-beams true)    ; good
(release-sharks {:laser-beams true} 2)  ; better, the configuration is the least variance argument
(release-sharks 2 {:laser-beams true})  ; bad

pbostrom

;; 1. top-level let
(let [state (atom 0)]
  (defn do-stuff1 []
    (swap! state inc))

  (defn do-stuff2 []
    (swap! state dec)))

;; 2. top-level atom
(def state (atom 0))

pbostrom

Interval Since Last Panic Report:  4179520 sec
Panics Since Last Report:          5
Anonymous UUID:                    1120CBDC-7AB8-0506-91A9-C2FD34C0D644

Tue Apr 22 10:56:08 2014
panic(cpu 2 caller 0xffffff8028d26fba): "negative open count (c, 16, 1)"@/SourceCache/xnu/xnu-2050.48.12/bsd/miscfs/specfs/spec_vnops.c:1813
Backtrace (CPU 2), Frame : Return Address
0xffffff8233a93be0 : 0xffffff8028c1d636 
0xffffff8233a93c50 : 0xffffff8028d26fba 
0xffffff8233a93c90 : 0xffffff8028d2be46 

pbostrom

(ns foo)

(defprotocol Foo
  (alpha [this a])
  (beta [this a]))

(ns bar
  (:require [foo :as f]))

(defrecord Bar []

pbostrom

(defn long-func-name [x y z] :bar)

(defn baz1 []
  (long-func-name (some-thing-arg1)
                  (some-thing-arg2) arg3))

(defn baz2 []
  (long-func-name (some-thing-arg1)
    (some-thing-arg2) arg3))

pbostrom

(define-key input-decode-map "\e[1;5A" [C-up])
(define-key input-decode-map "\e[1;5B" [C-down])
(define-key input-decode-map "\e[1;5C" [C-right])
(define-key input-decode-map "\e[1;5D" [C-left])

pbostrom

set-window-option -g xterm-keys on

pbostrom

(defn test29 
  "Write a function which takes a string and returns a new string
  containing only the capital letters."
  [f]
  [(= (f "HeLlO, WoRlD!") "HLOWRD")
   (empty? (f "nothing"))
   (= (f "$#A(*&987Zf") "AZ")])

(test29 identity)