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• Example-lexer

Lex-whitespace

Match whitespace to create a :whitespace token.

Signature

(lex-whitespace sin) → (mv tok sin)

Arguments

sin — The sin stobj.

Returns

tok — A whitespace token that contains all of the whitespace from the start of the input stream, or nil if there is no leading whitespace.
    Type (equal (token-p tok) (if tok t nil)).

sin — The remaining input stream, with the leading whitespace removed.

Definitions and Theorems

Function: lex-whitespace

(defun lex-whitespace (sin)
  (declare (xargs :stobjs (sin)))
  (declare (xargs :guard t))
  (let ((__function__ 'lex-whitespace))
    (declare (ignorable __function__))
    (b* (((mv match sin)
          (sin-match-charset* (whitespace-chars)
                              sin))
         ((unless match) (mv nil sin)))
      (mv (make-token :type :whitespace
                      :text match)
          sin))))

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

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

Theorem: lex-whitespace-progress-weak

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

Theorem: lex-whitespace-progress-strong

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

Theorem: lex-whitespace-reconstruction

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