(Comp.sys.hp48)
Item: 415 by jmorriso@ee.ubc.ca [John Paul Morrison]
  Subj: some utilities
  Date: Thu Dec 19 1991

Some little utilities I wrote in RPL code
by John Paul Morrison, jmorriso@ee.ubc.ca

ÚÄÄÄÄÄ¿
³ DDX ³
ÀÄÄÄÄÄÙ
Purely symbolic derivative, does not evaluate the result.
This works just like the builtin DER function/command, but it
ignores existing values of the variable.
Many people (sometimes myself) were annoyed at having to
purge a variable to calculate a symbolic derivative.

example: if X=0
'SIN(X)' 'X' DER will give 1 (in radians mode)
but  DDX will give 'COS(X)'
'X' will not be modified

ÚÄÄÄÄÄÄ¿
³ DNDX ³
ÀÄÄÄÄÄÄÙ
Take Nth derivative. uses DDX

ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ DATE\->MENU ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Puts the time and date in the menu key area.
Nice to add to a calender program

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³ SCRLGROB ³
ÀÄÄÄÄÄÄÄÄÄÄÙ
Loads a GROB into the display, where you can scroll it
Does not modify PICT
Press ON to exit
Based on HP Tools examples

ÚÄÄÄÄ¿
³ DD ³
ÀÄÄÄÄÙ
Bring up a catalog menu

By itself it's no big deal,
but if you use some of Joe Horn's tricks:

 ::
   Do1st/2nd+:    ( #3EE1A )
   ( insert contents of DD here )
   ( normal key action here     )
 ;

and assign this to a key, you will effectively get DD as a directory
browser, that can be called from within an editing session. That
way you can change directories while editing.

Here's how I use it:
It is assigned to BLUE-SHIFT MTH(key 21.3, since I don't have a printer)
normally it calls another program called KEYS, otherwise
it starts the directory browser; when editing.

Example application:
ÚÄÄÄÄÄÄÄ¿
³ DDKEY ³
ÀÄÄÄÄÄÄÄÙ
ASN to 21.3, works in USR mode
example only, unless you like my setup

ÚÄÄÄÄÄÄÄÄÄ¿
³ \->DISP ³
ÀÄÄÄÄÄÄÄÄÄÙ
Put a GROB in the display
doesn't destroy PICT

It's kind of a patch for \->LCD, since \->LCD
will load a GROB into the text display, but leaves
the menu keys displayed, which will hide part of your GROB

ÚÄÄÄÄÄ¿
³ TMF ³
ÀÄÄÄÄÄÙ
Turn menu keys off temporarily
Someone wanted this, so here it is.

You might need to run RECL to initialize
You do need to run RECL afterwards to recover
136 bytes allocated by the program.

ÚÄÄÄÄÄÄ¿
³ RECL ³
ÀÄÄÄÄÄÄÙ
Do a "reclaim" of the screen
Do this after turning menus off


I've been interested in electronics since high-school, and I
still can't remember resistor color codes! (except for the
mnemonic "Bad boys .... but Violet ..." which doesn't help
me calculate the values.

ÚÄÄÄÄÄÄÄÄ¿
³ RES\-> ³
ÀÄÄÄÄÄÄÄÄÙ
I wrote this part in RPL, not that it needed RPL, but the RPL
version is smaller, and a lot more elegantly coded than in user
language.
This lets you enter the colors, to find the value.

ÚÄÄÄÄÄÄÄÄ¿
³ \->RES ³
ÀÄÄÄÄÄÄÄÄÙ
Shows the color codes for a resistor, given a value
so when you're hunting through the junk drawer...
This does not give "preferred" values, so if if you
enter a weird resistor value, you will never see
that resistor in real circuit.