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Full Discussion: Gobsmacked by ksh93 floating point arithmetic.
Operating Systems OS X (Apple) Gobsmacked by ksh93 floating point arithmetic. Post 303024881 by wisecracker on Thursday 18th of October 2018 03:51:55 PM
Old 10-18-2018
Quote:
Originally Posted by Corona688
Interesting, a few obvious improvements.
  • You don't need $ on variable names inside (( ))
  • (( )) replaces [ ] for integer mathematics, especially float
  • The && construct will tremendously reduce redundancy here
  • You should use typeset to declare a local variable, otherwise you're unintentionally stomping on each other's ANGLE all the time
  • You should not be using global variables for all communication
  • You can make that giant equation one short loop
  • Not everything needs to be a function, many things are shorter and more readable as the single value they are
  • A bit more sanitization for negative input values
Apologies for any typos...

1: True but we had a discussion about it on this site WRT shellcheck and I decided I was going to keep '$' due to discrepancies of some combinations.

Here:
A $(( expression )) bug?

2: The ksh version is of 2007 vintage and I assumed double parentheses (in the method you have used them) to be unavailable, however...
3: I never even thought about the && construct as I had no idea my incarnation would even remotely give reasonably accurate results.
4: 'typeset' is duly noted and will be used in COSINE soon. Good point about stomping on its own variable. As this was a prototype that point hadn't crossed my mind.
5: I tend to use global variables a great deal, even in Python, my mind tends to work globally. <wink>
6: Using the 'set' statement like you have done is completely new to me and is cool. Logged in the old grey matter for future use.
7: True and AudioScope has the mixture.
8: Negative values; love it, nice-n-simple. I was more interested in my code snippet working and I never expected anyone to strip it and better it so quickly. I will now put your code in the script and take it from there.

Not sure whether to use a modified version of the sin() section of the code as a whole for COS(X) or use the SIN(X) script and call it as SIN(X+90) for the same result.

Will experiment and find out over the next day or so.

------ Post updated at 08:51 PM ------

Quote:
Originally Posted by Corona688
A version that doesn't need the table:

Code:
        F=1     # N factorial
        for ((N=1; N<=13; ))
        do
                (( SIN += (ANGLE**N)/F ))
                ((F *= ++N))
                ((F *= - ++N))
        done

Neat, but...
I don't quite understand how this works.
Surely ((F *= - ++N)) would overwrite ((F *= ++N)), if NOT then I don't understand why?
Please explain...
Last edited by wisecracker; 10-18-2018 at 05:18 PM.. Reason: No idea why a separate post has become an edit on a previuos one!
 

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