Re: Why did HP get rid of stack clear? Message #7 Posted by Karl Schneider on 22 June 2004, 2:37 a.m., in response to message #6 by Garth Wilson
"CLST" was a useful command, I think, primarily in programming in order to ensure "causality" (same inputs, same algorithm, and same initial state ==> same outputs every time) in programs that might utilize stack operations while assuming an initially empty stack.
(Certainly, 0 ENTER ENTER ENTER in "interactive mode" is easier than executing CLST from the 42S CLEAR menu or XEQ "CLST". However, CLST is a cleaner program instruction.)
The reason CL_Sigma did a stack clear on the pre-Pioneer RPN HP's was to help prevent sabotaged calculations of standard deviations caused by debris data in the y-stack when subsequently entering stat data. These calc's automatically performed Y-variable summations using the y stack values, and always calculated SD for Y-variables as well, whether or not 2-variable statistics was being performed.
The 32S/32SII/33S, however, allows the user to calculate X-variable and Y-variable statistics separately. Thus, bogus Y-data that was inadvertently utilized cannot bollix the SD calculations. So, clearing the stack beforehand is not of utmost importance; and, there's no room for "CLST" unde the CLEAR menu, anyway...
Alles klar? Probably not... ;-)
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