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Re: Favourite Pattern for Processing Zero, Once, Multiple

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"Shao Miller" <sha0.miller@gmail.com> wrote in message
news:kcpn8m$gvs$1@dont-email.me...
> On 1/11/2013 07:15, BartC wrote:

>> It's not clear what the roles of bar() and foo() are. Maybe one of those
>> returns the next translated character, but some more information is
>> needed. The whole thing seems a bit like a tokeniser, or at least has
>> some of the same problems to be solved.

> For the subsequent translation scenario I tried to describe, the caller is
> responsible for getting a single input character 'ic'.  However they do it
> should be opaque to the translating function, 'bar'.  The caller calls
> 'bar' to translate 'ic' to '*oc'.
>
>   extern return_type bar(state_type state, char ic, char * oc);
>
> 'bar' might not emit any output character '*oc' if it's not yet ready. In
> that case, the caller shouldn't work with '*oc'; shouldn't send it
> wherever output is going.

Your function seems to be deceptively simple, but it's not! It could be
used, for example, to translate one language to another.

But suppose it is kept simple, so that all it does is translate N characters
of input (N>=1) to M characters of output (M>=0).

It might not know the value of N either, until it's read the N'th (or even
subsequent) character (for example, to map repeated characters to just one
or zero occurrences).

One problem I can see is that both N and M could be very large, for various 
reasons, but let's say the state variables can cope with buffering unlimited 
numbers of input and/or output characters.

Then we're pretty much back to the dialog in your original post. I don't
know if there's any standard way of doing these things.

I can tell you that I probably wouldn't stick with the character-at-time
model, but allow a string to be returned.

I think (not having tried) the states can be reduced to just two: (1) bar is
waiting for the character to start the next block of N; (2) it is waiting
for the character to delimit this block. With (2), bar() *has* to be called
again until this pattern is complete, and it reverts to state (1). (But it's
also possible some patterns will never complete, and the caller needs a way
of terminating.)

After each call there will also be some output in the form of a string
(which can also be done by a callback on each character), of any length
including zero.

-- 
bartc 

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Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-10 17:53 -0500
  Re: Favourite Pattern for Processing Zero, Once, Multiple "BartC" <bc@freeuk.com> - 2013-01-10 23:26 +0000
    Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-10 18:49 -0500
      Re: Favourite Pattern for Processing Zero, Once, Multiple "BartC" <bc@freeuk.com> - 2013-01-11 00:23 +0000
  Re: Favourite Pattern for Processing Zero, Once, Multiple Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-11 03:20 +0000
    Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-11 00:38 -0500
      Re: Favourite Pattern for Processing Zero, Once, Multiple Bart van Ingen Schenau <bart@ingen.ddns.info.invalid> - 2013-01-11 12:10 +0000
        Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-11 13:37 -0500
      Re: Favourite Pattern for Processing Zero, Once, Multiple "BartC" <bc@freeuk.com> - 2013-01-11 12:15 +0000
        Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-11 13:56 -0500
          Re: Favourite Pattern for Processing Zero, Once, Multiple Fred K <fred.l.kleinschmidt@gmail.com> - 2013-01-11 11:15 -0800
            Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-11 14:28 -0500
          Re: Favourite Pattern for Processing Zero, Once, Multiple Greg Martin <greg@softsprocket.com> - 2013-01-11 11:22 -0800
            Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-11 15:23 -0500
              Re: Favourite Pattern for Processing Zero, Once, Multiple Greg Martin <greg@softsprocket.com> - 2013-01-11 13:09 -0800
          Re: Favourite Pattern for Processing Zero, Once, Multiple "BartC" <bc@freeuk.com> - 2013-01-11 22:09 +0000
          Re: Favourite Pattern for Processing Zero, Once, Multiple Paul N <gw7rib@aol.com> - 2013-01-12 04:49 -0800
            Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-13 20:30 -0500
  Re: Favourite Pattern for Processing Zero, Once, Multiple glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-11 21:02 +0000
  Re: Favourite Pattern for Processing Zero, Once, Multiple Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2013-01-13 20:28 +0200
    Re: Favourite Pattern for Processing Zero, Once, Multiple Shao Miller <sha0.miller@gmail.com> - 2013-01-13 16:12 -0500

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