I'm experimenting around a custom Lisp evaluator (reading Lisp in Small Pieces) in CLJS with Lumo.
Is there a way to ask the user for a string and then process it? Like the shell has read or Python has input.
Thanks.
You could use nodejs readline package:
(def readline (js/require "readline"))
(def rl (.createInterface readline #js {:input (.-stdin js/process) :output (.-stdout js/process)}))
(.question rl "ok?" pr)
Related
I am trying to use AWS Amplify Authentication lib in a re-frame app.
The lib provides a higher order component withAuthenticator which is supposed to wrap the main view of your app. I am trying to use reactify-component and adapt-react-class but unfortunately I get the following error:
Uncaught TypeError: Failed to construct ‘HTMLElement’: Please use the ‘new’ operator, this DOM object constructor cannot be called as a function.
(defn main-panel []
[:div
[:h1 "Hello" ]])
(def root-view
(reagent/adapt-react-class
(withAuthenticator
(reagent/reactify-component main-panel))))
(defn ^:dev/after-load mount-root []
(re-frame/clear-subscription-cache!)
(aws-config/configure)
(re-frame/dispatch-sync [::events/initialize-db])
(reagent/render [root-view]
(.getElementById js/document "app")))
Any help is appreciated
I had this issue with reagent + amplify.
Solved it with 2 changes, but I'm unsure if both are needed
#1 Change output of the google closure compiler to es6 (or higher). Amplify seems to use es6 features that Cannot be polyfilled.
This is for shadow-cljs (shadow-cljs.edn), but this should be possible for other build systems as well.
{:builds {:app {:compiler-options {:output-feature-set :es6}}}}
Disclaimer: I switched to shadow-cljs from lein-cljsbuild since I could not get lein-cljsbuild to respect the configuration for es6 output.
#2 Use functional components.
In reagent 1.0.0-alpha1 and up you can change the compiler to produce functional components by default.
(ns core
(:require
[reagent.core :as r]))
(def functional-compiler (r/create-compiler {:function-components true}))
(r/set-default-compiler! functional-compiler)
There are other ways to make functional components. Check the documentation if you don't like, or can't use, this approach.
In my ClojureScript code I am requiring a JavaScript module called seedrandom which is in the node_modules folder, like this:
(ns something.core
(:require ["seedrandom" :as rnd]))
(js/console.log (.quick (rnd "x")))
According to the seedrandom documentation it is intended for both nodejs and the browser, and I've previously included and used it successfully in ClojureScript code via a <script> tag, confirming it works in the browser.
Running this cljs file in lumo on the command line works well and outputs a deterministically random number.
When I try to use this same cljs file in my Reagent frontend project I see the following error:
Compiling build :app to "public/js/app.js" from ["src" "env/dev/cljs"]...
events.js:183
throw er; // Unhandled 'error' event
^
Error: module not found: "crypto" from file /home/chrism/dev/something/node_modules/seedrandom/seedrandom.js
at onresolve (/home/chrism/dev/something/node_modules/#cljs-oss/module-deps/index.js:181:30)
...
Inside seedrandom.js we see the following:
// When in node.js, try using crypto package for autoseeding.
try {
nodecrypto = require('crypto');
} catch (ex) {}
Clearly this code is intended to ignore the built-in nodejs crypto module when running in the browser. The problem, as far as I can tell, is that the ClojureScript compiler does not know that - it sees that require('crypto') and tries to pull it into the compilation phase, but can't find it because it's a nodejs built-in.
Is there some way I can tell the compiler to ignore that particular require? Or can I shim the 'crypto' module somehow? What is the cleanest way to solve this?
Note: I have previously experienced this same issue with JavaScript modules which check for the fs node module. Hope we can find a general solution to use again in future. Thanks!
Relevant versions: [org.clojure/clojurescript "1.10.520"] and [reagent "0.8.1"].
This answer is related, asking a similar question from the perspective of Google Closure, which ClojureScript uses, but I'm looking for an answer I can use specifically with cljs.
How can I get the Clojurescript namespace I am in from within a clojurescript program? I want to do this do provide certain debug information (it only needs to work in dev mode)
Namespaces are not first class in ClojureScript as they are in Clojure. There's absolutely no way to get the namespace at runtime. It is possible to get this information at macroexpansion time if you're not afraid of accessing some the ClojureScript compiler internals. There should probably be an API for this - but we're not there yet.
You can get the name of the current namespace with this trick, which takes advantage of :: creating a namespaced symbol for you in the current namespace:
(namespace ::x)
You probably don't want to use that value for anything, because if the code is compiled the internal representation will change. If you want to live dangerously, then in the browser you can then access the js object that holds the namespace like this:
(reduce (fn [ns n] (aget ns n))
js/window
(clojure.string/split (namespace ::x) #"\."))
During macro-expansion you can access &env and retrieve namespace information from the :ns key like this:
(:ns &env)
(:name (:ns &env))
This only works at macro-expansion/compile time and not at runtime.
You can try this
(apply str (drop-last 2 (str `_)))
Is there an equivalent of Common Lisp's *features* in Clojure, so you can detect the OS and other environment configuration? Or do I just go through the Java API for that?
Probably use the Java API. It's easy enough, no sense re-inventing the wheel.
user> (System/getProperty "os.name")
"Linux"
user> (System/getProperty "os.version")
"2.6.36-ARCH"
user> (System/getProperty "os.arch")
"amd64"
To add to Brian Carper's answer, you could easily create a map of system properties via the Java API and bind it to the symbol features:
(def *features* {
:name (System/getProperty "os.name"),
:version (System/getProperty "os.version"),
:arch (System/getProperty "os.arch")})
Which gives you this structure, for example:
{:name "Windows 7", :version "6.1", :arch "x86"}
Then access a property in any one of the following ways:
(:name *features*)
(*features* :name)
(get *features* :name)
Whichever floats your boat.
Other answers are handling how to get the system info from Java pretty well. If you want more help interpreting it, here are some examples of how Terracotta did that:
VendorVmSignature
VmVersion
Vm
I've been trying to create a user-defined exception in Clojure, and have been having all sorts of problems. I tried the method outlined here:
http://en.wikibooks.org/wiki/Clojure_Programming/Concepts#User-Defined_Exceptions
(gen-and-load-class 'user.MyException :extends Exception)
But that doesn't seem to work in Clojure 1.2 (or I'm doing something wrong...). My environment is Clojure 1.2, Emacs, and lein swank.
Thanks for your help!
Rather than generating custom classes, there are two much simpler ways to use custom exceptions:
Use slingshot - this provides custom throw+ and catch+ macros that let you throw and catch any object, as well as exceptions.
In clojure 1.4 and above, you can use clojure.core/ex-info and clojure.core/ex-data to generate and catch a clojure.lang.ExceptionInfo class, which wraps a message and a map of data.
Using this is straightforward:
(throw (ex-info "My hovercraft is full of eels"
{:type :python-exception, :cause :eels}))
(try (...)
(catch clojure.lang.ExceptionInfo e
(if (= :eels (-> e ex-data :cause))
(println "beware the shrieking eels!")
(println "???"))))
Or in a midje test:
(fact "should throw some eels"
(...)
=> (throws clojure.lang.ExceptionInfo
#(= :eels (-> % ex-data :cause))))
Make a file src/user/MyException.clj (where src is on CLASSPATH) containing:
(ns user.MyException
(:gen-class :extends java.lang.Exception))
Check the value of *compile-path* at the REPL. Make sure this directory exists and is on CLASSPATH. Create the directory if it doesn't exist; Clojure won't do so for you.
user> *compile-path*
"/home/user/foo/target/classes/"
user> (System/getProperty "java.class.path")
".......:/home/user/foo/target/classes/:......."
Compile your class:
user> (compile 'user.MyException)
user.MyException
If it worked, in *compile-path* you should now have files something like this:
/home/user/foo/target/
/home/user/foo/target/classes
/home/user/foo/target/classes/user
/home/user/foo/target/classes/user/MyException.class
/home/user/foo/target/classes/user/MyException__init.class
/home/user/foo/target/classes/user/MyException$loading__4410__auto__.class
Restart your Clojure REPL / JVM to load these classes. Again, make sure these new class files are on CLASSPATH. Now you should be able to use your class:
user> (user.MyException.)
#<MyException user.MyException>
FWIW, unless you are creating a custom exception for interop reasons you may want to consider using clojure.contrib.condition instead. It comes with a precompiled custom exception that you piggy-back custom data onto using it's API. I've been able to avoid creating many custom exceptions by using it instead. The docs are here:
http://clojure.github.com/clojure-contrib/condition-api.html