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    • Oct-digit

    Oct-digit-fix

    Fixer for oct-digit.

    Signature
    (oct-digit-fix x) → fixed-x
    Arguments
    x — Guard (oct-digitp x).
    Returns
    fixed-x — Type (oct-digitp fixed-x).

    Definitions and Theorems

    Function: oct-digit-fix

    (defun oct-digit-fix (x)
      (declare (xargs :guard (oct-digitp x)))
      (mbe :logic (if (oct-digitp x) x (char-code #\0))
           :exec x))

    Theorem: oct-digitp-of-oct-digit-fix

    (defthm oct-digitp-of-oct-digit-fix
      (b* ((fixed-x (oct-digit-fix x)))
        (oct-digitp fixed-x))
      :rule-classes :rewrite)

    Theorem: oct-digit-fix-when-oct-digitp

    (defthm oct-digit-fix-when-oct-digitp
      (implies (oct-digitp x)
               (equal (oct-digit-fix x) x)))