Utils for PRINTing and READing CL standard hash-tables, inspired by Haskell's fromList

gistfile1.lisp

(in-package :cl-user)

(defpackage :m-utils
  (:use :cl)
  (:export :from-list :print-ht))

(in-package m-utils)

(defmacro from-list (list &rest params)
  "A hash-table generator inspired by Haskell's fromList."
  (let ((ht (gensym))
        (item (gensym))
        (key (gensym))
        (value (gensym)))
    `(let ((,ht (make-hash-table ,@params)))
       (dolist (,item ,list)
         (destructuring-bind (,key ,value) ,item
           (setf (gethash ,key ,ht) ,value)))
       ,ht)))

(defun print-ht (ht &optional (stream *standard-output*))
  "Print a READable version of a hash-table"
  (prin1 `(from-list
           ,(loop for key being the hash-keys of ht
                  collect `(,key ,(gethash key ht)))
           :test ',(hash-table-test ht)
           :rehash-size ,(hash-table-rehash-size ht)
           :rehash-threshold ,(hash-table-rehash-threshold ht))
         stream))

;; since standard print function for hash-table are already
;; unreadable, this should be backward compatible
(defmethod print-object ((object hash-table) stream)
  (print-ht object stream))

;; all keys and values are PRINTable with print-ht and READable with
;; from-list, as long as this vals and keys are PRINTable and READable

;; (defvar test-map (from-list '(("ok" t) ("nop" t)) :test 'equal))
;; (gethash
;;  "ok"
;;  (eval (read-from-string "(from-list '((\"ok\" t) (\"nop\" '())) :test 'equal)")))