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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: How to use a struct with qsort()?
Date: Sat, 26 Oct 2019 02:11:35 -0700
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Ike Naar <ike@sdf.lonestar.org> writes:
> On 2019-10-25, Manfred <noname@add.invalid> wrote:
>> On 10/19/2019 10:26 PM, DFS wrote:
>>> int primes[26] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41,
>>>           43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101}; 
>>> char *charset = "abcdefghijklmnopqrstuvwxyz";
>> Since primes and charset are strictly coupled, it is a good idea to 
>> enforce consistency of their sizes as in:
>> #include <assert.h>
>> static const unsigned int primes[] =
>> {
>>    2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41,
>>    43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101
>> };
>> static const char charset[] = "abcdefghijklmnopqrstuvwxyz";
>> static_assert(sizeof(primes)/sizeof(primes[0]) == 
>> (sizeof(charset)/sizeof(charset[0])-1),
>>      "charset and primes mismatch");
>
> Why the "-1" ?
> primes[] and charset[] have the same number of elements (26).

No, charset[] has 27 elements.  It's initialized from a string literal,
so there's a trailing '\0'.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */