A better alist macro

with-alist-access.el

;;; with-alist-access.el --- a better alist macro

;; This is free and unencumbered software released into the public domain.

;;; Commentary:

;; Usage example:

;;     (let ((student '((id . 1332412)
;;                      (name . ((first . "Student")
;;                               (last  . "Example")))))
;;           (teacher '((subject . math)
;;                      (full-name . "Teacher Example"))))
;;       (with-alist-access
;;         (list student.name.first teacher.full-name)))

;; Result:

;;     => ("Student" "Teacher Example")

;;; Code:

(require 'cl-lib)

(defun with-alist-access--transform-symbol (symbol)
  "Convert a symbol containing dots into an alist lookup."
  (let ((split (mapcar #'intern (split-string (symbol-name symbol) "\\."))))
    (if (= 1 (length split))
        symbol
      (cl-reduce (lambda (object key)
                   `(cdr (assq ',key ,object))) split))))

(defun with-alist-access--transform-sexp (sexp)
  "Transform a single s-expression for `with-alist-access'."
  (cons (car sexp)
        (cl-loop for arg in (cdr sexp) collect
                 (cl-typecase arg
                   (list   (with-alist-access--transform-sexp arg))
                   (symbol (with-alist-access--transform-symbol arg))
                   (otherwise arg)))))

(defmacro with-alist-access (&rest body)
  "Convert all variables of the form foo.bar into an alist lookup on foo.
This macro works on nested"
  (declare (indent 0))
  `(progn
     ,@(mapcar #'with-alist-access--transform-sexp body)))

(provide 'with-alist-access)

;;; with-alist-access.el ends here