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Massimo Gnerucci · 09-07-2018, 11:32 AM

A blast from the past.

While browsing a 1996 backup of an old computer of mine, I found a directory with my dabbling exercises in Personal REXX 2.0 in the late 80ies.
And, lo and behold, there I found some examples - bundled with the program - from Namir's review of the product on BYTE.

Here's one:

Code:

/*______________________________________________________________________________*​/

/*ROOT.REX Accompanies the review, "Personal REXX" by Namir Clement Shammas, Byte, January 1988, page 167*/

/*______________________________________________________________________________*​/

/* Root seeing using Newton's method */

/* Personal REXX version */

NUMERIC DIGITS 10

NUMERIC FORM SCIENTIFIC

SAY 'Enter expression (of variable X) '

pull fstring

fstring = 'Y = '||fstring

SAY 'Enter guess and accuracy '

pull guess accr

diff = 2 * accr

iter = 0

MAXITER = 30

DO WHILE ABS(diff) > accr

  IF ABS(guess) > 1.0 THEN h = 0.01 * guess; ELSE h = 0.01

  SAY 'guess = ' guess

  diff = 2.0 * h * FF(guess) / (FF(guess + h) - FF(guess - h))

  guess = guess - diff

  iter = iter + 1

  IF iter > MAXITER THEN diff = 0

END

SAY ' '

SAY ' '

SAY 'Root = ' guess

SAY ' '

SAY 'Number of iterations = ' iter

EXIT

FF: PROCEDURE EXPOSE fstring

 arg X

 INTERPRET fstring

 /* variable Y is part of the interpreted fstring */

 RETURN Y

Serendipity... :)

Zaphod · 09-08-2018, 06:34 PM

BYTE

Ahhhhh ......Great magazine , brings back memories

Duane Hess · 09-09-2018, 05:36 AM

Holy cow!

Used to manage a VM/ESA system. Used EXEC2 & REXX a lot. Often wrote my own quick & dirty stuff in REXX. Always impressed me between REXX and XEDIT/macros the amount of power you could have; realatively easily.

Is Personal REXX still available? Wouldn't mind a full(er) version of XEDIT that ran under Windows or DOS also. Guess I could search.

How often I missed the VM system; though somewhat perculiar it was.

Massimo Gnerucci · 09-09-2018, 10:34 AM

(09-09-2018 05:36 AM)Duane Hess Wrote: Holy cow!

Used to manage a VM/ESA system. Used EXEC2 & REXX a lot. Often wrote my own quick & dirty stuff in REXX. Always impressed me between REXX and XEDIT/macros the amount of power you could have; realatively easily.

I started on VM/CMS and VM EXEC.

(09-09-2018 05:36 AM)Duane Hess Wrote: Is Personal REXX still available? Wouldn't mind a full(er) version of XEDIT that ran under Windows or DOS also. Guess I could search.

You could try Regina REXX or Open Object REXX.
Regarding XEDIT, there's KEDIT (but hurry up, if you really want it ;) )

(09-09-2018 05:36 AM)Duane Hess Wrote: How often I missed the VM system; though somewhat perculiar it was.

I loved it too.

toml_12953 · (This post was last modified: 09-10-2018 12:12 PM by toml_12953.)

(09-09-2018 10:34 AM)Massimo Gnerucci Wrote: You could try Regina REXX or Open Object REXX.
Regarding XEDIT, there's KEDIT (but hurry up, if you really want it )

I loved it too.

I just sent the company an email asking them to release it to the Public Domain. Many other companies have done this when they stopped selling software. There's a benefit for hobbyists and no downside for the company.

toml_12953 · (This post was last modified: 09-10-2018 12:15 PM by toml_12953.)

(09-07-2018 11:32 AM)Massimo Gnerucci Wrote: A blast from the past.

While browsing a 1996 backup of an old computer of mine, I found a directory with my dabbling exercises in Personal REXX 2.0 in the late 80ies.
And, lo and behold, there I found some examples - bundled with the program - from Namir's review of the product on BYTE.

Here's one:

Code:

/*______________________________________________________________________________*/ /*ROOT.REX Accompanies the review, "Personal REXX" by Namir Clement Shammas, Byte, January 1988, page 167*/ /*______________________________________________________________________________*/ /* Root seeing using Newton's method */ /* Personal REXX version */ NUMERIC DIGITS 10 NUMERIC FORM SCIENTIFIC SAY 'Enter expression (of variable X) ' pull fstring fstring = 'Y = '||fstring SAY 'Enter guess and accuracy ' pull guess accr diff = 2 * accr iter = 0 MAXITER = 30 DO WHILE ABS(diff) > accr IF ABS(guess) > 1.0 THEN h = 0.01 * guess; ELSE h = 0.01 SAY 'guess = ' guess diff = 2.0 * h * FF(guess) / (FF(guess + h) - FF(guess - h)) guess = guess - diff iter = iter + 1 IF iter > MAXITER THEN diff = 0 END SAY ' ' SAY ' ' SAY 'Root = ' guess SAY ' ' SAY 'Number of iterations = ' iter EXIT FF: PROCEDURE EXPOSE fstring arg X INTERPRET fstring /* variable Y is part of the interpreted fstring */ RETURN Y

Serendipity...

Has anyone tried to run this in Regina REXX? I get an error:

Code:

Enter expression (of variable X)

2*x^2+3*x-12

Enter guess and accuracy

5 .0001

guess =  5

    38 +++       INTERPRET fstring

    22 +++    diff = 2.0 * h * FF(guess) / (FF(guess + h) - FF(guess - h))

Error 64 running "D:\Program Files\rexx.org\Regina\demo\NewtonsRoot.rexx", line 38: [Syntax error while parsing]

Error 64.1: [Syntax error at line 38]

Of course I haven't run REXX since my OS/2 days so I may be entering the data wrong.

Thomas Klemm · 09-10-2018, 12:52 PM

(09-10-2018 12:14 PM)toml_12953 Wrote: Has anyone tried to run this in Regina REXX? I get an error:
(…)

Of course I haven't run REXX since my OS/2 days so I may be entering the data wrong.

I assume you have to write that expression as:

Code:

2*x**2+3*x-12

Cheers
Thomas

Massimo Gnerucci · 09-10-2018, 01:26 PM

(09-10-2018 12:14 PM)toml_12953 Wrote: Has anyone tried to run this in Regina REXX? I get an error:

Thomas is right (as usual...)

Code:

D:\ReginaREXX391w64>regina.exe root.rex

Enter expression (of variable X)       

2 * X**2 + 3 * X - 12                  

Enter guess and accuracy               

5 0.001                                

guess =  5                             

guess =  2.695652174                   

guess =  1.925113151                   

guess =  1.814140206                   

guess =  1.811738817                   

Root =  1.811737692                    

Number of iterations =  5

Geoff · 09-10-2018, 03:07 PM

(09-08-2018 06:34 PM)Zaphod Wrote: BYTE

Ahhhhh ......Great magazine , brings back memories

Always loved BYTE.

What would Jerry Pournelle have to say about current computers?

Geoff

Thomas Klemm · 09-10-2018, 04:00 PM

We can use the Complex-Step Derivative Approximation mentioned in Derivatives on HP 42S to calculate with a single subroutine call both \(f(x)\) and \(f'(x)\) in Newton's method:

\(x_{n+1}=x_{n}-{\frac {f(x_{n})}{f'(x_{n})}}\)

Code:

00 { 34-Byte Prgm }

01▸LBL "NEWTON"

02 STO "x"

03 RCL "h"

04 COMPLEX

05 XEQ "FF"

06 COMPLEX

07 RCL÷ "h"

08 ÷

09 STO- "x"

10 RCL "x"

11 END

For the equation \(2x^2+3x-12=0\) of the given example this program can be used:

Code:

00 { 19-Byte Prgm }

01▸LBL "FF"

02 2

03 RCL× ST Y

04 3

05 +

06 ×

07 12

08 –

09 END

Initialisation

1E-8
STO "h"

Iteration

5
XEQ "NEWTON"
y: 2.30434782609
x: 2.69565217391

R/S
y: 0.77053902071
x: 1.92511315320

R/S
y: 1.10972947392E-1
x: 1.81414020581

R/S
y: 2.40138878229E-3
x: 1.81173881703

R/S
y: 1.12553786619E-6
x: 1.81173769149

R/S
y: 2.47260969077E-13
x: 1.81173769149

Cheers
Thomas

toml_12953 · 09-11-2018, 12:35 PM

(09-10-2018 12:52 PM)Thomas Klemm Wrote:
(09-10-2018 12:14 PM)toml_12953 Wrote: Has anyone tried to run this in Regina REXX? I get an error:
(…)

Of course I haven't run REXX since my OS/2 days so I may be entering the data wrong.

I assume you have to write that expression as:

Code:

2*x**2+3*x-12

Cheers
Thomas

Thank you! The exponentiation symbol (**) had dropped from my memory entirely!