Clojurians Log v2

How can I make a repl using clojure? Any help? THis is my current code but doesn't work 😞

(defn print-prompt [s]
  (print (str "\n" s)))

(defn get-user-input
  []
  (read-line))

(defn repl-loop
  []
  (while true
    (do
      (print "REPL>>")
      (print-prompt (get-user-input)))))

you need to invoke the reader and then eval.

(println (eval (read-string (get-user-input)))) ReadEvalPrintLoop

@sunchaesk This is how Clojure's REPL is implemented: https://github.com/clojure/clojure/blob/38524061dcb14c598c239be87184b3378ffc5bac/src/clj/clojure/main.clj#L456-L466 -- the source code can be an interesting read sometimes when you're trying to figure out how to do similar things.

@seancorfield Thank you so much I never really thought about it 😄

@seancorfield sorry to bother, but could there be like a simple code that works? and maybe I will try improving from it? I just can't seem to make a simple one work

@dpsutton wrote a working code in the comment just above

https://clojurians.slack.com/archives/C053AK3F9/p1623036648368800

user=> (while true (println (eval (read-string (read-line)))))
(+ 1 1)
2
(let [x 1] (+ x 2))
3

oh shoot didn't see that

thank you so much

What macros do which functions cannot do, I meant (when to use macros and when to use functions)

https://purelyfunctional.tv/mini-guide/when-to-use-a-macro-in-clojure/

Macros allow you to capture expressions before you're evaluated.

(f x)

(defn f-function [x]
  (+ x x))

(defmacro f-macro [x]
  (cond (= x 'x) :x
        (= x 'y) :y
        :else `(f-function ~x)))

(f-function 10)
;; => 20

(f-macro 10)
;; => 20

(let [x 10]
  (f-function x))
;; => 20

(let [x 10]
  (f-macro x))
;; => :x

This may be an overly general question but I am starting on a project where I want to wrap a Javascript library and use it in Clojurescript. The Library (libraries - since there are sub libraries) is https://github.com/accordproject/cicero It is available on NPM-- It is basically a parsing library that parses text and returns json - I want to use the json in my Clojure/Clojurescript project - There is a version that has been adopted for Lambda https://github.com/accordproject/aws-qldb-lambda but I want to basically create a Clojurscript SDK - possibly to publish as a library - and use it in my project — I know I have a long way to go but is there a tutorial? or an example I could go by for doing something like this - I have gone through the Shadow-cljs documentation but I wanted something more specific to wrapping an existing library — I know there are several examples with java

Does anyone know any good animations that show how `apply` works in Clojure? Something like this? https://jstutorial.medium.com/map-filter-and-reduce-animated-7fe391a35a47

apply is fundamentally a different sort of thing from map, filter, and reduce

I am not sure I have a good way to describe the different though, maybe apply is a control flow operation, it is function application reified. map, filter, reduce are dataflow operations.

https://norvig.com/lispy.html defines a little lisp in python, which doesn't have apply, but if you look at the definition of eval, it contains an implementation of apply

apply is probably one of those things that you will find when you really need it. e.g. you have [1 2 3] and max, how do you call max on that list (assume that you can't use reduce for whatever reason)?

if you really wanted to you could go through and change all your function calls in your programs from (f x y) to (apply f [x y])

oh look: https://borkdude.github.io/re-find.web/?args=max%20%5B1%202%203%5D&ret=3 ;)

I don't care for the comparison there, because it suggests some relationship between reduce and apply

reduce is firmly a construct of the language, given a language without it, if you have first class functions you can write it. apply is the definition of your language bleeding into the language (sort of like eval, and in fact eval is a superset of apply).

https://github.com/borkdude/sci/blob/master/src/sci/impl/evaluator.cljc#L314 like here is apply in the eval for sci