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Chris3020
Chris3020
Last Activity: Mar 17 '23, 08:46 AM
Joined: May 1 '22
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  • Chris3020
    started a topic Autoscale large integer calculations to avoid overflow
    in C

    Autoscale large integer calculations to avoid overflow

    I have some code that will (frequently) generate S sets of C count of relatively large integers N.
    I need the set with the lowest product.

    int S ranges 7 .. 15 (run-time constant defined at startup).
    int C ranges 2 .. 13 (defined by caller for each call).
    int N ranges 0 .. 2000 (values cannot be predicted by caller).
    …any N==0 in a set aborts the generation of that set (S—)
    …if all...
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    • Chris3020
      replied to C Validating >=1 numeric argv[]
      in C
      ...sorry for radio-silence: some stuff came up in the real-world.

      Turned out that I was the only user for the C-version of the utility!
      A friend asked for something to calculate the product of the first N prime-numbers after some number X.
      ...run-times of a few micro-seconds did not overcome his dislike of the command-line.
      Once the algorithm was ironed out in C it got translated into VBA! He's happier with that....
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      • Chris3020
        replied to C Validating >=1 numeric argv[]
        in C
        @Luuk

        I admit to being crazy, but I'm not quite crazy enough to devote 1000 lines of code to input validation for an integer!
        Was just looking for a neat way that didn't involve a huge (1000 lines...) library designed to handle every nit-picky facet of argv[] parsing.

        Since posting, I remembered abs() ...doh!

        Input validation is now simple:
        Code:
          unsigned this = abs(atoi(argv[2]));
        ...
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        Last edited by Chris3020; Aug 17 '22, 07:23 PM. Reason: delete un wanted <space>

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        • Chris3020
          started a topic C Validating >=1 numeric argv[]
          in C

          C Validating >=1 numeric argv[]

          I have a simple utility expecting three command-line arguments:
          ./myutil -k 123 45

          argv[1] is a text flag of some sort: memcmp() against allowed flags; works!

          argv[2] and argv[3] need to sit in unsigned 32-bit integers and are required to be >= 1.

          For now I'm using:
          strstr() to look for "-" ...and assuming absence of "-" means +ve number-as-string.
          atoi() to...
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          • Chris3020
            replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
            in C
            @zmbd:
            I think we leave it as is :)

            +1 vote. Chris
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            • Chris3020
              replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
              in C
              silly error:

              Code:
              static void dict_free(void) {
  for (int i = 0; i < MAX_WORDLEN; ++i)...  // should be:  i < MAX_WORDLEN[B]+1[/B];
              See more | Go to post
              Last edited by zmbd; May 8 '22, 10:30 PM.

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              • Chris3020
                replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                in C
                Bah!
                It just happened again:

                open page: missing some (not all) underscores!
                refresh page: hey ho, underscores are back!
                eh?

                Is it me?
                MacBook Air (M1 2020)
                MacOS BigSur 11.6.5
                Safari 15.4 (16613.1.17.1.1 3, 16613)
                // this is not the appropriate forum in which to discuss the most absurd version nomenclature on the planet!

                Or you?

                Chris
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                • Chris3020
                  replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                  in C
                  !!ASHAMED!! that you found 30 residual <tab> ...I went through line-by-line manually replacing <tab> with <space><space >.
                  I was using Mac TextEdit for this exercise (an app that I don't normally use, so I didn't try auto find/replace).
                  My only hope for salvation is that those errant <tab> were between meaningful char and \n.

                  !!BAFFLED!! by the underscores.
                  Looking again now, they...
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                  • Chris3020
                    replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                    in C
                    Thanks zmbd.
                    Had a go at fixing the <tab> issue.
                    Chris

                    ...just noticed: code seems to have dropped some underscores! between copy and paste.
                    ...ah no! some underscores don't show, but copy from posted code to text-editor and they are back again.
                    [#r!§
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                    Last edited by Chris3020; May 8 '22, 09:39 AM. Reason: "disappeared" underscores! ...are actually (invisibly) there.

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                    • Chris3020
                      replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                      in C
                      Apparently I can't edit stuff inside code ... /code tags.
                      Ho hum!

                      Chris
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                      • Chris3020
                        replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                        in C
                        mmm; straight copy/paste code from BBEdit is __NOT__ a good idea: the <tab>s went crazy. Sorry!
                        ...will try to edit!
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                        • Chris3020
                          replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                          in C
                          I went with 2)
                          It was very close to my "latest effort" above.

                          I didn't like the extra 8 bytes per word in dicts[] of 1), though it was "pretty".

                          Thanks for all your suggestions, Chris

                          Current test rig looks like this:

                          []
                          Code:
                          #include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_WORDLEN 10 // maximum
                          ...
                          See more | Go to post
                          Last edited by zmbd; May 8 '22, 03:16 PM. Reason: [Chris3020[Reason: kill all the wretched <tab>s]] [Z{had a go at it - removed another 30 tabs not sure about anu missing _ }]

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                          • Chris3020
                            replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                            in C
                            Mmmmmm interesting!
                            **words just has to be more correct in the struct: I have a dozens of variations using ** (and hundreds of errors/warnings to go with).
                            I will study (and experiment with) your stuff over the weekend.
                            Thank you!
                            Chris

                            My latest effort is below. It still uses *words in the struct, it compiles, it even works (...but it is not pretty):
                            Code:
                            #include <stdio.h>
#include
                            ...
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                            • Chris3020
                              replied to 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                              in C
                              Thanks for the suggestion ...sorry, not tested yet - but it makes sense.
                              Will experiment tomorrow morning.

                              Is there no way to get this done with a single malloc per dicts[n] ?
                              ...many thousands of malloc() seems less "efficient" .

                              All this happens in a "setup-phase", so it doesn't need to be fast ...run-times for the application that uses dicts[] can be seconds to hours depending on...
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                              • Chris3020
                                started a topic 3D Array of (Array of Strings) -- my malloc attempts fail miserably
                                in C

                                3D Array of (Array of Strings) -- my malloc attempts fail miserably

                                I'm trying to make a sort-of-dictionary (don't think "hashmap" when you see that d-word, my dictionary is just simple lists of words in a 3D array)

                                Code:
                                #define MAX_WORDLENGTH 20

struct dict{
	int wordcount;
	char **words;
};

struct dict dicts[MAX_WORDLENGTH + 1]; // +1 to get an index for MAX_WORDLENGTH
                                e.g. dicts[7] is the struct dict for 7-letter words (7 excludes...
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