In JVM Clojure, Exceptions are for operating errors ("something went wrong") and Assertions are for programmer and correctness errors ("this program is wrong").
An assert might be the right tool if throwing an Exception isn't enough. Use
them when the assertion failing means
| (ns flexi-clock | |
| (:import (java.time Clock Duration Instant ZonedDateTime))) | |
| (defn clock | |
| "potential library function (e.g. in tick or tempo). | |
| This just implements the platform Clock - which works because non-test code only uses that API. | |
| Any manipulation of time (which happens in testing code) is done via changing | |
| what get-instant and get-zone return" | |
| [get-instant get-zone] |
Simple experiment to test the effects of different techniques and options on application start up time
The goal of CDS is to reduce the startup time of the JVM by loading from a pre-processed archive of Java classes and JVM metadata that is used during the initialization process. https://dev.java/learn/jvm/cds-appcds/
| (defn stateful-map | |
| "Returns a stateful transducer similar to `clojure.core/map-indexed` that | |
| transforms each item with `(f state <the item>)` where `state` is built by | |
| applying `state-building-fn` to the previous state (starting with `init`) and | |
| the transformed item. | |
| Ex., re-implementing map-indexed: | |
| ```clojure | |
| (sequence (stateful-map vector (fn build-state [idx _] (if idx (inc idx) 5))) \"abc\") | |
| ; => ([nil \\a] [5 \\b] [6 \\c]) |
Short write up on using REPL when developing UIs in ClojureScript.
Everyone's standard approach to hot-reloading is to use a tool (Figwheel or shadow-cljs) that reloads changed namespaces automatically. This works really well: you change the code, the tool picks up changed files, compiles namespaces and dependants, notifies REPL client which then pulls in compiled changes, and re-runs a function that re-renders UI.
The other approach is to use ClojureScript's REPL directly and rely only on eval from the editor. This more or less matches Clojure style workflow. This approach might be useful when you don't want tools overhead or hot-reloading becomes slow for you or you just used to this style of interactions. Also changing code doesn't always mean that you want to reload all the changes. On the other hand it is very easy to change a couple of top-level forms and forget to eval one of them.
| #!/bin/sh | |
| #_( | |
| #_DEPS is same format as deps.edn. Multiline is okay. | |
| DEPS=' | |
| {:deps {clj-time {:mvn/version "0.14.2"}}} | |
| ' | |
| #_You can put other options here | |
| OPTS=' |
A list of commonly asked questions, design decisions, reasons why Clojure is the way it is as they were answered directly by Rich (even when from many years ago, those answers are pretty much valid today!). Feel free to point friends and colleagues here next time they ask (again). Answers are pasted verbatim (I've made small adjustments for readibility, but never changed a sentence) from mailing lists, articles, chats.
How to use:
| (ns deep-merge-spec | |
| (:require [midje.sweet :refer :all] | |
| [util :as u])) | |
| (fact (u/deep-merge {:one 1 :two 2} | |
| {:one 1 :two {}}) | |
| => {:one 1 :two {}}) | |
| (fact (u/deep-merge {:one 1 :two {:three 3 :four {:five 5}}} | |
| {:two {:three {:test true}}}) |
