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Example-lexer

Lex1

Lex a single token from the input stream.

Signature
(lex1 sin) → (mv tok sin)
Arguments: sin — The sin stobj, which we assume still has text remaining.
Guard (not (sin-endp sin)).
Returns: tok — The first token from the start of the input stream, or nil on failure.
Type (equal (token-p tok) (if tok t nil)).; sin — The remaining input stream, with the leading token removed.

Definitions and Theorems

Function: lex1

(defun lex1 (sin)
  (declare (xargs :stobjs (sin)))
  (declare (xargs :guard (not (sin-endp sin))))
  (let ((__function__ 'lex1))
    (declare (ignorable __function__))
    (b* ((char1 (sin-car sin))
         ((when (char-in-charset-p char1 (whitespace-chars)))
          (lex-whitespace sin))
         ((when (char-in-charset-p char1 (letter-chars)))
          (lex-id/keyword sin))
         ((when (sin-matches-p "//" sin))
          (lex-comment sin)))
      (lex-punctuation sin))))

Theorem: return-type-of-lex1.tok

(defthm return-type-of-lex1.tok
  (b* (((mv ?tok ?sin) (lex1 sin)))
    (equal (token-p tok) (if tok t nil)))
  :rule-classes :rewrite)

Theorem: lex1-progress-weak

(defthm lex1-progress-weak
  (mv-let (tok new-sin)
          (lex1 sin)
    (declare (ignorable tok new-sin))
    (<= (len (strin-left new-sin))
        (len (strin-left sin))))
  :rule-classes ((:rewrite) (:linear)))

Theorem: lex1-progress-strong

(defthm lex1-progress-strong
  (mv-let (tok new-sin)
          (lex1 sin)
    (declare (ignorable tok new-sin))
    (implies tok
             (< (len (strin-left new-sin))
                (len (strin-left sin)))))
  :rule-classes ((:rewrite) (:linear)))

Theorem: lex1-reconstruction

(defthm lex1-reconstruction
  (b* (((mv tok new-sin) (lex1 sin)))
    (implies tok
             (equal (append (explode (token->text tok))
                            (strin-left new-sin))
                    (strin-left sin)))))