Rexx code tends to run slowly. The key to a fast scripts are the efficient algorithms. I have been collecting such algorithms. It isn't a trivial job to translate algorithms from various pseudocodes or programming languages as Ada, ALGOL, BASIC, C, FORTRAN, Modula, Pascal, PL/1, into the useful code in the Rexx language.
'There is the disadvantage of not knowing all languages,' said Conceil, 'or the disadvantage of not having one universal language.'
Jules Verne Twenty Thousand Leagues Under the Sea
The Album may be useful as a reference, since it contains an organized collection of algorithms. All of this are expressed in the Rexx language. You can try copy and paste this routines from browser into an editor, direct into a concrete program (in detail: Technique: Universal Unit). ATTENTION! Please, when you see the following fragment on the two lines, then you have to decrease font in your browser (Thanks Doug Rickman email@example.com from NASA for this warning).
do J = K - 1 to 1 by -1; SubSet = A.J SubSet; end
After the downloading
of my album you can change the properties of fonts by the arrangements of the AATSTYLE.CSS
The Album can be useful in a college course on algorithms as well in beginning courses of the programming in the Rexx language. The Album is an experiment: I use the Rexx language in an explanations and descriptions of algorithms, too. Hence I say things like "Its time complexity is FORMAT(3*N/2-2,,0) comparisons" or "pattern P. occurs with shift S in text T. if
0<=S<=N-M and if T.SpJ=P.J, where SpJ indicates S+J, for J=1,...,M". The Album proves that the Rexx language is the suitable vehicle for presentation a set useful algorithms in clean, succint, and uniform code.
Note - We therefore reserve the special symbol lgN to denote a logarithm with base
17th September 2001
Short circuiting in Rexx?
12th September 2001
Test environment by Walter Pachl ...
24th August 2001
I finished rewriting and repairing of the whole album
3th August 2001
New solution 3_1 in Technique: Universal unit by Tobias Herp
28th July 2001
Offline version of my www pages with Album of Algorithms and Techniques is available on CD of OS2.cz as freeware
1st July 2001
P+n trick by Walter Pachl added in Reflexio
18th June 2001
Walter Pachl repaired the last digits in the V variable in
LN2 and PICONST functions.
12th March 2001
The functions for calculating of the area of a triangle - numerically unstable HERON and numerically stable ATRIAN.
4th March 2001
After reading Kahan's Mathematics Written in Sand I changed the function REPOWER:
if P = "" then P = 9; P = P + 4; numeric digits P
22nd February 2001
Danny De Wilde sent me mail with question How to compute function real power? It inspired me to creating the function REPOWER.
1st December 2003
James Barbetti sent me subprogram HEAPSORT_RADIX3 in Visual Basic.
[Album as ZIP file]
There is the Album as ZIP file, Version 2nd April 2018.
For the comparison of published algorithms I use as a measuring instrument my PC with 6x86MX-PR233 processor and 32MB RAM, Mark Hessling's REXX-Regina_0_08g 4.80 31 Jul 1999, since 12 August 2000 REXX-Regina_2.0 4.80 4 May 2000, and since 26 June 2001 REXX-Regina_2.2 4.80 17 Jun 2001 interpreter, Microsoft Windows 98 4.10.1998.
Roderic A. Davis, New York
the D2R function
Tobias Herp, Bad Homburg, Germany
added new solution 3_1 into Technique: Universal unit
Walter Pachl, Vienna, Austria
Test environment and his P+n trick in Reflexio
Doug Rickman, Global Hydrology and Climate Center, MSFC, NASA
the SPLINE and SPLINT functions
Gerard Schildberger, Hankinson, North Dakota
the CEILING, FLOOR functions
Michael Adams, Cologne, Germany
repaired the subroutine
PRIMES and the function PRIMALITY_TEST
Walter Pachl, Vienna, Austria
found errors in LN2 and PICONST functions. He studied the whole album step by step - 78 pages! -, verified the programs in OS/2 environment; found error in the HEAPSORT subprogram; improved the definition of general selection problem and corrected some errors. Walter's mails inspired me to rewriting the whole album (June - August 2001).
George W. Perry, Flintstone, Georgia
reported a bug in the INTERPOLATION_SEARCH
Gerard Schildberger, Hankinson, North Dakota
simplified the PI and SQRT functions. He called my attention to the error in LN10 function. I would like to thank Gerard for reading the whole Album and correcting many mistakes in 50(!) pages. I used all his helpful comments,
corrections, and suggestions that resulted in many improvements my English in the
Danny De Wilde, Belgium
inspired me to creating the function REPOWER.
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