;;; binary.el --- Binary exercise (exercism)

;;; Commentary:

;;; Code:

(require 'cl)

(defun to-decimal-helper (str)
  (cl-loop with result = 0
           for c across str
           do (setq result (+ (- c ?0) (* 2 result)))
           finally return result))

(defun to-decimal (str)
  (if (string-match "[01]+" str)
      (to-decimal-helper str)
    0))

(provide 'binary)
;;; binary.el ends here