Get the alternative field from a expression-sum-field.
(expression-sum-field->alternative x) → alternative
This is an ordinary field accessor created by fty::defprod.
Function:
(defun expression-sum-field->alternative$inline (x) (declare (xargs :guard (expressionp x))) (declare (xargs :guard (equal (expression-kind x) :sum-field))) (let ((__function__ 'expression-sum-field->alternative)) (declare (ignorable __function__)) (mbe :logic (b* ((x (and (equal (expression-kind x) :sum-field) x))) (identifier-fix (std::da-nth 2 (cdr x)))) :exec (std::da-nth 2 (cdr x)))))
Theorem:
(defthm identifierp-of-expression-sum-field->alternative (b* ((alternative (expression-sum-field->alternative$inline x))) (identifierp alternative)) :rule-classes :rewrite)
Theorem:
(defthm expression-sum-field->alternative$inline-of-expression-fix-x (equal (expression-sum-field->alternative$inline (expression-fix x)) (expression-sum-field->alternative$inline x)))
Theorem:
(defthm expression-sum-field->alternative$inline-expression-equiv-congruence-on-x (implies (expression-equiv x x-equiv) (equal (expression-sum-field->alternative$inline x) (expression-sum-field->alternative$inline x-equiv))) :rule-classes :congruence)
Theorem:
(defthm expression-sum-field->alternative-when-wrong-kind (implies (not (equal (expression-kind x) :sum-field)) (equal (expression-sum-field->alternative x) (identifier-fix nil))))