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Example-lexer

Lex-comment

Match comment characters to create an :comment token.

Signature
(lex-comment sin) → (mv tok sin)
Arguments: sin — The sin stobj.
Returns: tok — A comment token taken from the start of the input stream, or nil if the input stream does not start with a comment.
Type (equal (token-p tok) (if tok t nil)).; sin — The remaining input stream, with the leading comment removed.

Definitions and Theorems

Function: lex-comment

(defun lex-comment (sin)
  (declare (xargs :stobjs (sin)))
  (declare (xargs :guard t))
  (let ((__function__ 'lex-comment))
    (declare (ignorable __function__))
    (b* ((comment-p (sin-matches-p "//" sin))
         ((unless comment-p) (mv nil sin))
         ((mv match sin)
          (sin-match-through-lit (newline-string)
                                 sin))
         ((when match)
          (mv (make-token :type :comment :text match)
              sin))
         ((mv match sin)
          (sin-match-everything sin)))
      (mv (make-token :type :comment :text match)
          sin))))

Theorem: return-type-of-lex-comment.tok

(defthm return-type-of-lex-comment.tok
  (b* (((mv ?tok ?sin) (lex-comment sin)))
    (equal (token-p tok) (if tok t nil)))
  :rule-classes :rewrite)

Theorem: lex-comment-progress-weak

(defthm lex-comment-progress-weak
  (mv-let (tok new-sin)
          (lex-comment sin)
    (declare (ignorable tok new-sin))
    (<= (len (strin-left new-sin))
        (len (strin-left sin))))
  :rule-classes ((:rewrite) (:linear)))

Theorem: lex-comment-progress-strong

(defthm lex-comment-progress-strong
  (mv-let (tok new-sin)
          (lex-comment sin)
    (declare (ignorable tok new-sin))
    (implies tok
             (< (len (strin-left new-sin))
                (len (strin-left sin)))))
  :rule-classes ((:rewrite) (:linear)))

Theorem: lex-comment-reconstruction

(defthm lex-comment-reconstruction
  (b* (((mv tok new-sin) (lex-comment sin)))
    (implies tok
             (equal (append (explode (token->text tok))
                            (strin-left new-sin))
                    (strin-left sin)))))