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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)))))