Lisp lexing using using alexa

lexing.lisp

;;;; https://github.com/rigetticomputing/alexa

(ql:quickload "alexa")

#|
(defpackage :blang
  (:use :common-lisp :alexa))

(in-package :blang)
|#

(use-package :alexa)

(deftype token ()
  `(cons keyword t))

(defun tok (type &optional val)
  (cons type val))

(define-string-lexer arith-lexer
  "Make a lexical analyzer for arithmetic expressions."
  ((:num "\\d+")
   (:name "[A-Za-z][A-Za-z0-9_]*"))
  ("{{NAME}}" (return (tok :variable (intern $@))))
  ("{{NUM}}"  (return (tok :number (parse-integer $@))))
  ("[+*/-]"   (return (tok :operator (intern $@ 'keyword))))
  ("\\("      (return (tok :left-paren)))
  ("\\)"      (return (tok :right-paren)))
  ("\\s+"     nil))

(defun lex-line (string)
  (loop :with lexer := (arith-lexer string)
        :for tok := (funcall lexer)
        :while tok
	:collect tok))

(print (lex-line "2*(x+1)/z"))