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Primitive-narrowing-conversions

Long-to-char

Narrowing conversion from long to char [JLS14:5.1.3].

Signature
(long-to-char operand) → result
Arguments: operand — Guard (long-valuep operand).
Returns: result — Type (char-valuep result).

Definitions and Theorems

Function: long-to-char

(defun long-to-char (operand)
  (declare (xargs :guard (long-valuep operand)))
  (b* ((x (long-value->int operand)))
    (char-value (loghead 16 x))))

Theorem: char-valuep-of-long-to-char

(defthm char-valuep-of-long-to-char
  (b* ((result (long-to-char operand)))
    (char-valuep result))
  :rule-classes :rewrite)

Theorem: long-to-char-of-long-value-fix-operand

(defthm long-to-char-of-long-value-fix-operand
  (equal (long-to-char (long-value-fix operand))
         (long-to-char operand)))

Theorem: long-to-char-long-value-equiv-congruence-on-operand

(defthm long-to-char-long-value-equiv-congruence-on-operand
  (implies (long-value-equiv operand operand-equiv)
           (equal (long-to-char operand)
                  (long-to-char operand-equiv)))
  :rule-classes :congruence)