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From: Ed Morton <mortonspam@gmail.com>
Newsgroups: comp.lang.awk
Subject: Re: Nitpicking the code (Was: Experiences with match() subexpressions?)
Date: Mon, 14 Apr 2025 18:55:22 -0500
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On 4/14/2025 1:53 PM, Janis Papanagnou wrote:
> On 14.04.2025 20:20, Kenny McCormack wrote:
>> In article <vtgtkr$3br8e$1@dont-email.me>,
>> Ed Morton  <mortonspam@gmail.com> wrote:
>> ...
>>>      data = "R=\"R=r1,R=r2\",R=r2,R=r3,E=e"
>>>      nf = patsplit(data, arr, /[RE]=([^,]*|"([^"]|"")*")/)
>>>      delete arr
>>>      for ( i in arr ) {
>>>          sub(/[^=]+=/, "", arr[i])
>>>      }
>>
>> This can't be right, since if the sequence:
>>      delete arr
>>      for (i in arr) ...
>> can't possibly do anything.  I.e., the for statement will be a no-op, since
>> the array is empty at that point.

Yeah, remove that `delete arr`, it's not necessary since `patsplit()` 
will delete `arr` before populating it and `delete arr` in that location 
would break the code.

>>
>>> or any awk:
>>>
>>>      data = "R=\"R=r1,R=r2\",R=r2,R=r3,E=e"
>>>      nf = 0
>>>      delete arr
>>>      while ( match(data, /[RE]=([^,]*|"([^"]|"")*")/, a) ) {
>>>          arr[++nf] = substr(data, RSTART+2, RLENGTH-2)
>>>          data = substr(data, RSTART+RLENGTH)
>>>      }
>>
>> I believe "delete arr" (without an index, hence removing the entire array)
>> is an "extension".  I can't quite quote chapter and verse, but I note that
>> "man mawk" explicitly mentions that mawk supports this syntax, thereby
>> implying that it isn't "standard".  Of course, gawk supports it as well.

`delete arr` is defined by the current POSIX standard 
(https://pubs.opengroup.org/onlinepubs/9799919799/utilities/awk.html) as 
equivalent to `for (index in array) delete array[index]` but for years 
prior to that [almost?] every maintained awk supported `delete arr` anyway.


>> So, if by "any awk", you mean "strictly standard", then, well, you can see
>> where I am going with this.
> 
> I seem to recall that a standard way to clear an array could be using
>    split("", arr)

`split("", arr)` was the defacto "standard" way to delete an array's 
content without looping before `delete arr` was adopted by POSIX. In all 
seriousness if anyone is using an awk that doesn't support `delete arr` 
then they need to get a new awk as who knows what other features it 
might be lacking.

	Ed.

> for example. To my taste it looks a bit clumsy, not as nice as using
> 'delete', but well, whatever one prefers.
> 
> Janis
>