Lisp

_posts/2022-10-13-lisp.md

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+---
+layout: post
+title: Lisp (Clojure)
+date: 2022-10-13 16:28:00+0200
+categories: programming-language
+---
+
+# Lisp
+
+Lisp is a family of programming languages with many dialects in it.
+
+Most popular are Clojure, Common Lisp, Racket.
+
+## Syntax
+
+There are a few special symbols: ` ()'"[]`.
+
+You can write numbers and strings as you usually do in other programming
+languages.
+
+
+```clojure
+100500 ; comment about integer
+-1.5   ; flating point number
+22/7   ; ratio
+"ruby" ; string
+\e     ; character
+#"\d"  ; regex
+```
+
+## Symbols
+
+```clojure
+def               ; symbol
++                 ; symbol
+java.lang.Math/PI ; namespaced symbol
+:with             ; keyword
+:with/regex       ; keyword with namespace
+```
+
+## Literal collections
+
+```clojure
+'(1 2 3)     ; list
+[1 2 3]      ; vector
+#{1 2 3}     ; set
+{:a 1, :b 2} ; map
+```
+
+### Atoms
+
+Atom is either a literal (numeric or string) of or a symbol.
+You can think of a symbol as of name.
+
+```clojure
+(defn factorial [n]
+  (if (< n 2)
+      1
+      (* n (factorial (- n 1)))))
+```
+
+### S-expressions
+
+Symbolic expression is an atom or list of other s-exrpressions in braces.
+
+```clojure
+(list 3 4 5 (* 3 2) 7) ; s-expression
+; list and * are symbols
+; 2 3 4 5 7 - numbers 
+; (* 3 2) - s-expression
+```