Newsgroups: comp.sys.hp48
From: Khanh-Dang <kd@fr.invalid>
Subject: Re: Hiding things
Date: Thu, 9 Feb 2006 17:32:02 +0100
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Here is a little UserRPL I wrote in order to hide things into an array
of real numbers.

----------------------------------
%%HP: T(3)A(R)F(.);
DIR
  Ahide
  \<< \-> ob arry
    \<< arry
      IF DUP TYPE 3. \=/
      THEN # 202h DOERR
      END \->H DUP SIZE 5. - ob
BYTES SWAP DROP 2. * + R\->B A\->H
6. SWAP REPL ob \->H + H\->
    \>>
  \>>
  Aunhide
  \<< \-> arry
    \<< arry
      IF DUP TYPE 3. \=/
      THEN # 202h DOERR
      END BYTES SWAP DROP 2. *
arry SIZE LIST\->
      IF 2. ==
      THEN * 16. * 30. +
      ELSE 16. * 25. +
      END
      IF DUP2 \=/
      THEN arry \->H UNROT 1. +
SWAP SUB H\-> 1.
      ELSE DROP2 0.
      END
    \>>
  \>>
END
----------------------------------

BYTES gives # A89Eh and 412.5.

The two programs use some commands (H->, ->H and A->H) of library 256
so they only work on HP49.

To hide any object into an array, put the object and the array on the
stack and launch Ahide. An array is left on the stack. This array looks
like the one you gave to Ahide, but it contains your object.

To recall a hidden object, just put the array on the stack and launch
Aunhide. If the array does contain a hidden object, then the object and
1. are returned ; 0 is returned in the other case.