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• Parser

Token-expression-start-p

Check if an optional token may start an expression.

Signature

(token-expression-start-p token? gcc) → yes/no

Arguments

token? — Guard (token-optionp token?).

gcc — Guard (booleanp gcc).

Returns

yes/no — Type (booleanp yes/no).

Looking at the grammar, an expression always starts with (or is) a cast expression, which is either a unary expression or a cast expression proper. The latter starts with an open parenthesis, but that is already covered by the possible starts of primary expressions.

So we just define this as a synonym of token-unary-expression-start-p, to make it clearer that we are talking about all expressions and not just unary expressions.

Definitions and Theorems

Function: token-expression-start-p

(defun token-expression-start-p (token? gcc)
  (declare (xargs :guard (and (token-optionp token?)
                              (booleanp gcc))))
  (let ((__function__ 'token-expression-start-p))
    (declare (ignorable __function__))
    (token-unary-expression-start-p token? gcc)))

Theorem: booleanp-of-token-expression-start-p

(defthm booleanp-of-token-expression-start-p
  (b* ((yes/no (token-expression-start-p token? gcc)))
    (booleanp yes/no))
  :rule-classes :rewrite)

Theorem: non-nil-when-token-expression-start-p

(defthm non-nil-when-token-expression-start-p
  (implies (token-expression-start-p token? gcc)
           token?)
  :rule-classes :forward-chaining)