Groups > comp.lang.java.programmer > #37783

Re: Two exceptions

Path	csiph.com!news.bbs.geek.nz!.POSTED.agency.bbs.geek.nz!not-for-mail
From	Patrick Roemer <sangamon@netcologne.de> (Patrick Roemer)
Newsgroups	comp.lang.java.programmer
Subject	Re: Two exceptions
Date	Sat, 09 Dec 2017 13:47:32 +1200
Organization	fsxNet Usenet Gateway \| bbs.geek.nz/#fsxNet
Message-ID	<2326571928@f38.n261.z1.binkp.net> (permalink)
References	<1735587349@f38.n261.z1.binkp.net>
Mime-Version	1.0
Content-Type	text/plain; charset=us-ascii
Content-Transfer-Encoding	7bit
Injection-Info	news.bbs.geek.nz; posting-host="M6YmRdZYyc42DJk0lNlt/X4dpP4dzvceBNabSmESN3E"; logging-data="10956"; mail-complaints-to="abuse@news.bbs.geek.nz"
User-Agent	VSoup v1.2.9.47Beta [95/NT]
X-Comment-To	Victor Porton
X-MailConverter	SoupGate-Win32 v1.05
Xref	csiph.com comp.lang.java.programmer:37783

Show key headers only | View raw

Responding to Victor Porton:
> The main reason I chose to use exceptions for this, is to allow parse()
> method to return the result of parsing (not a boolean value). For example
> result of parsing an integer may return "long".
>
> Can you propose another alternative? It is to be easily programmable (if I
> find handling exceptions too slow, I always can rewrite my program).
>
> Oh, I see, you proposed to return "null" instead of my ParseException. It
> however also seems to me not a quite good solution, because returning null
> may be a non-exceptionable situation (as for a missing optional object in
> the parsed resource).

Instead of null, you could use (potentially nested) java.util.Optional for
both, signaling failed parse attempts and optional productions.

failure: empty
success (plain): of(x)
success (optional, non-match): of(empty) success (optional, match): of(of(x))

Preferably, you could introduce a specialized union type for the parse result,
allowing you to propagate detail information in the failure case.

See the Reply type here, for example:

https://github.com/jon-hanson/parsecj#types

Best regards,
Patrick

Thread

Two exceptions Victor Porton <porton@narod.ru> (Victor Porton) - 2017-12-09 00:53 +1200
  Re: Two exceptions Eric Sosman <esosman@comcast-dot-net.invalid> (Eric Sosman) - 2017-12-08 18:21 +1200
    Re: Two exceptions Victor Porton <porton@narod.ru> (Victor Porton) - 2017-12-09 01:55 +1200
      Re: Two exceptions Eric Sosman <esosman@comcast-dot-net.invalid> (Eric Sosman) - 2017-12-09 07:39 +1200
        Re: Two exceptions Victor Porton <porton@narod.ru> (Victor Porton) - 2017-12-10 02:39 +1200
          Re: Two exceptions Victor Porton <porton@narod.ru> (Victor Porton) - 2017-12-10 02:46 +1200
          Re: Two exceptions Kiwi User <martin@mydomain.invalid> (Kiwi User) - 2017-12-10 00:52 +1200
            Re: Two exceptions Kiwi User <martin@mydomain.invalid> - 2017-12-10 21:50 +0000
      Re: Two exceptions Patrick Roemer <sangamon@netcologne.de> (Patrick Roemer) - 2017-12-09 13:47 +1200
  Re: Two exceptions Arne Vajhøj <arne@vajhoej.dk> (Arne Vajhøj) - 2017-12-08 18:49 +1200
    Re: Two exceptions v_borchert@despammed.com (Volker Borchert) (Volker Borchert) - 2017-12-09 07:53 +1200
  Re: Two exceptions ram@zedat.fu-berlin.de (Stefan Ram) (Stefan Ram) - 2017-12-09 16:15 +1200
    Re: Two exceptions Eric Sosman <esosman@comcast-dot-net.invalid> (Eric Sosman) - 2017-12-09 14:55 +1200
      Re: Two exceptions Patrick Roemer <sangamon@netcologne.de> (Patrick Roemer) - 2017-12-11 15:09 +1200
        Re: Two exceptions Victor Porton <porton@narod.ru> - 2017-12-12 11:14 +0200

csiph-web