Re: Question on the behavior of length()

[Ed Morton]

Wolfgang - I'll let someone more versed in the internal workings of awk 
address the "why"s and "what ifs" if they like as I'd just be guessing 
and don't care to test other scenarios but regarding "the script", of 
course I just mean the part of the script executing the impacted code, 
i.e. the part using that index.

    Ed.

On 12/11/2023 7:06 AM, Wolfgang Laun wrote:
> That's interesting; I must have missed this in the documentation. - 
> What causes the switch from fast to slow? Would an index such as ToS = 
> -42 result in a speed reduction? What happens if a string as index is 
> introduced late in the game? Will all accesses to integer keys be 
> slowed down?
>
> Also, you wrote "makes /the script/ run about 3 times slower". Is it 
> true that these accesses to a single array affect the entire script?
>
> -W
>
> On Mon, 11 Dec 2023 at 13:55, Ed Morton <mortoneccc@comcast.net> wrote:
>
>     Using a string `"tos"` instead of a number `0` for the top of
>     stack index makes the script run about 3 times slower. You can
>     always do something like `Tos=0` and `x[Tos]` if you like.
>
>          Ed.
>
>     On 12/11/2023 6:45 AM, Wolfgang Laun wrote:
> >     Call it x["tos"] and x["doc"] to avoid me being confused and
> >     having to remember what is what.
> >     -W
> >
> >     On Mon, 11 Dec 2023 at 13:38, Ed Morton <mortoneccc@comcast.net>
> >     wrote:
> >
> >         Just a suggestion regarding calling `length()` for
> >         push()/pop() stack
> >         operations:
> >
> >         On 12/10/2023 8:18 AM, Christian Schmidt wrote:
> >         > Hi all,
> >         >
> >         > First of all I'd like to state that I do not consider the
> >         following
> >         > necessarily a bug; however I'd like to discuss the current
> >         > implementation, and have not found a better place to do so.
> >         >
> >         > My issue is that I can't use
> >         >
> >         > x[length(x)] = y
> >         >
> >         > e.g. to emulate to push to a stack, without explicitly
> >         converting x
> >         > into an array first, e.g. by "delete x".
> >
> >         No need to call `length(x)` for every push()/pop(), you can
> >         implement a
> >         stack by storing it's top index in `x[0]` (or some other unused,
> >         probably negative, index instead if you prefer):
> >
> >               function push(x,y) { x[++x[0]] = y }
> >               function pop(x) { delete x[x[0]--] }
> >
> >         As well as not having the problem you described that also
> >         allows you to
> >         use other unused indices to store other attributes about the
> >         stack, e.g.
> >         a description like `x[-1] = "this is a stack of connection
> >         requests"`,
> >         which you couldn't do if you were relying on `length(x)` to
> >         tell you the
> >         index of the top of the stack.
> >
> >         Regards,
> >
> >              Ed.
> >
> >
> >
> >     -- 
> >     Wolfgang Laun
>
>
>
> --
> Wolfgang Laun