Re: Which newsgroup for json parsing?

Malcolm McLean ha scritto:

On 16/05/2024 20:21, bart wrote:

On 16/05/2024 19:53, Scott Lurndal wrote:

=?UTF-8?Q?Josef_M=C3=B6llers?= <josef@invalid.invalid> writes:

On 16.05.24 18:27, Mikko wrote:

On 2024-05-08 13:04:56 +0000, Josef Möllers said:
>

Hi all,
>
I am trying to parse a json string received through MQTT from a
"Shelly Plug S", e.g.
{"id":0, "source":"button", "output":true, "apower":0.0,
"voltage":237.9, "current":0.000,
"aenergy":{"total":0.000,"by_minute":[0.000,0.000,0.000],"minute_ts":1715172119},"temperature":{"tC":41.1, "tF":106.0}}
>
I am trying to use libjson-glib but I can't figure out what to use as
the first argument to json_gobject_from_data()!
I am also looking at libjson-c but cannot find any examples that could
guide me.
>
Thanks in advance,

>
Sometimes it is easier to make a parser than to use an existing one.
In this case I might try LEX.
>

>
Sorry to be nitpicking, but lex is a "lexical analyzer" aka a "scanner",
it can only recognize tokens, eg the brackets, quotes, identifiers etc,
but not structures.
"yacc" (or its "bison" equivalent" would be a parser but definitely too
heavy.
>
What one could do would be to use LEX to recognize the tokens and the
write a recursive descent parser in plain C.

>
I've done full expression parsing and subsequent evaluation with
lex (or flex).  No parser needed.
>

>
You've done 'full expression PARSING', then you say 'No PARSER needed'.
>
A bit contradictory?
>
Clearly parsing IS needed, so either you've used LEX from code that acts as a parser, or it does more than just recognise tokens.
>

Yes.
 I took Ben's advice and completely rewrote my XML parser wirh a formal lexer and recursive descent grammar. It was good idea, even though XML is simple enough to get away with a ad hoc approach. Similarly, with JSON. once you've lexed into identifiers, values, and curly and square btackets, the grammar is so simple that you almost don't notice that you are writing a parser.
   --
Check out Basic Algorithms and my other books:
https://www.lulu.com/spotlight/bgy1mm
 

Don't you think it is overkill to use a compiler of compilers to parse a
Json?  The function I wrote for parse the Json is just 140 code lines in
C, while I found examples with much more bulky with lex & yacc.