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• Hex

Hexify

Convert numbers into readable hex strings.

(hexify x) is a dumb but useful printing utility for displaying numbers in hex. It is typically used in cw statements, e.g.,:

ACL2 !> (cw "foo is ~s0~%" (str::hexify (1- (expt 2 32))))
foo is #uxFFFF_FFFF
NIL
ACL2 !>

The #ux is for compatibility with the ACL2::sharp-u-reader.

See also nat-to-dec-string which converts numbers into decimal strings (without underscores) and binify which is like hexify but for binary instead of hex.

Usage

(hexify x) always returns a stringp.

x must be an integer, string, or symbol; otherwise a hard-error will be caused.

Normally x is an integer. In this case, we convert it into an msb-first hex string with an underscore inserted every four characters. This makes it easier to read long values.

When x is a string we just return it unchanged.

When x is a symbol we just return its name.

Definitions and Theorems

Function: hexify

(defun hexify (x)
 (declare (xargs :guard t))
 (cond
  ((integerp x)
   (b*
    ((xsign (< x 0))
     (xabs (abs x))
     (chars (explode-atom xabs 16))
     (nice-chars
       (list*
            #\# #\u #\x
            (append (and xsign '(#\-))
                    (cons (first chars)
                          (insert-underscores (nthcdr 1 chars)))))))
    (implode nice-chars)))
  ((symbolp x) (symbol-name x))
  ((stringp x) x)
  (t (prog2$ (er hard? 'hexify
                 "Unexpected argument ~x0.~%" x)
             ""))))

Subtopics

Insert-underscores