I highly recommend “The Joy of Clojure” or “programming Clojure” for a real answer to this question, I can reproduce a short snip-it of the motivations for each: start by watching this video on the notion of Identity and/or studying here. Refs are for Coordinated Synchronous access to “Many Identities”. Atoms are for Uncoordinated synchronous … Read more
Actually, there is a way! (comment (defn hey [] (“Hey there!”)) Check me out! ) Just wrap your comments in (comment ..) 🙂 Have fun!
classic recursion (watch this, it blows stack) (defn exp [x n] (if (zero? n) 1 (* x (exp x (dec n))))) tail recursion (defn exp [x n] (loop [acc 1 n n] (if (zero? n) acc (recur (* x acc) (dec n))))) functional (defn exp [x n] (reduce * (repeat n x))) sneaky (also blows … Read more
reduce and apply are of course only equivalent (in terms of the ultimate result returned) for associative functions which need to see all their arguments in the variable-arity case. When they are result-wise equivalent, I’d say that apply is always perfectly idiomatic, while reduce is equivalent — and might shave off a fraction of a … Read more
Try: /(?!.*bar)(?=.*foo)^(\w+)$/ Tests: blahfooblah # pass blahfooblahbarfail # fail somethingfoo # pass shouldbarfooshouldfail # fail barfoofail # fail Regular expression explanation NODE EXPLANATION ——————————————————————————– (?! look ahead to see if there is not: ——————————————————————————– .* any character except \n (0 or more times (matching the most amount possible)) ——————————————————————————– bar ‘bar’ ——————————————————————————– ) end of … Read more
Here’s the Clojure documentation for Keywords and Symbols. Keywords are symbolic identifiers that evaluate to themselves. They provide very fast equality tests… Symbols are identifiers that are normally used to refer to something else. They can be used in program forms to refer to function parameters, let bindings, class names and global vars… Keywords are … Read more
A function can have multiple signatures if the signatures differ in arity. You can use that to supply default values. (defn string->integer ([s] (string->integer s 10)) ([s base] (Integer/parseInt s base))) Note that assuming false and nil are both considered non-values, (if (nil? base) 10 base) could be shortened to (if base base 10), or … Read more
(map vector ‘(1 2 3) ‘(4 5 6)) does what you want: => ([1 4] [2 5] [3 6]) Haskell needs a collection of zipWith (zipWith3, zipWith4, …) functions, because they all need to be of a specific type; in particular, the number of input lists they accept needs to be fixed. (The zip, zip2, … Read more
They all have a lot in common: Dynamic languages Strongly typed Compiled Lisp-style syntax, i.e. code is written as a Lisp data structures (forms) with the most common pattern being function calls like: (function-name arg1 arg2) Powerful macro systems that allow you to treat code as data and generate arbitrary code at runtime (often used … Read more
There are several reasons why one should not use EVAL. The main reason for beginners is: you don’t need it. Example (assuming Common Lisp): EVALuate an expression with different operators: (let ((ops ‘(+ *))) (dolist (op ops) (print (eval (list op 1 2 3))))) That’s better written as: (let ((ops ‘(+ *))) (dolist (op ops) … Read more