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C parser ramblings, language design, etc

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From "Rod Pemberton" <boo@fasdfrewar.cdm>
Newsgroups alt.os.development
Subject C parser ramblings, language design, etc
Date Fri, 11 Sep 2015 19:11:50 -0400
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You would think that C, being created long ago, would be very easy
to parse with truly simple techniques, but things like optional
braces, 'while' used as both 'while' and 'do-while', i.e., which
'while' goes with 'do' when nested, base types comprising multiple
words, e.g., "long long", implicit int's, no keyword for typedef
usage, conflict with implicit int's and typedef's, ... etc all
complicate very simple C parsers.

E.g., since braces are optional in C, there isn't much useful
information for parsing, from statements like this:

do while(x--); while(x--);

That's confusing for a human and a simple parser.  It could be
recognized by both as either of these:

do { while(x--); } while(x--);
do {} while (x--); while(x--);

Which 'while' goes with the 'do'?  Only the first one is correct,
but how do you determine that from the braceless syntax above?
You get a 'while' prior to the 'while' you need.

Technically, the second example needs a semicolon, but that
doesn't help any with properly parsing the braceless example.

'while' is overloaded or ambiguous.  It means two different
things at different places, and somehow the parser or compiler
must distinquish and keep track of which 'while' goes with
which 'do'.  Nesting can throw the dual-keyword do-while loop
tracking out of whack.  Adding nested while just complicates
it further.  You almost need a stack and a state-machine.

That would've been much simpler to parse and emit code for if a
different keyword was used at the bottom of the loop or if the
condition was placed at the top of the loop for a do-while.
I.e., this is much easier to parse, since the 'while' keyword
isn't overloaded and it's easier to match paired 'do' and 'end':

do end(x--); while(x--);
do while(x--); end(x--);

Now, you know that every end is at the same scope as the 'do'
and you're not going to have "spurious" 'end's' inbetween.

/* condition syntax at top of bottom test/exit loop */
do(x--); { while(x--); }

That's even simpler.

I think the goal for any language should not only be LALR(1)
but also be able to be compiled in a single-pass with no
backtracking and with exceptionally easy parsing.  That's why
my language uses space delimited parsing, like Forth, with
character directed parsing.  I.e., a character in front of
each keyword, operator, etc in the language, tells the parser
what is coming next.

E.g., the hello world program for my language:

^main
{
   $"Hello_World!" ~puts
}

I.e., '^' for declaring a procedure, '~' for calling a
procedure, etc.  The parser doesn't have to determine that
"main" is a procedure or an identifier or that it's being
declared here, or that "puts" is a procedure which is being
called, or that "Hello_World" is a string, etc.  The character
directive tells it that.  Save info.  It's like a built-in
AST, somewhat.  I also went to a little bit of extra work
to support curly braces without following that pattern, which
would've required something to follow a brace.  Unfortunately,
I just realized that I should've provided for a C style
semicolon too ';' for multipled statements per block.

I also did some work on my larger C parser project.  I merged
in a bunch of similar code from other projects which helped
to fill the program out somewhat more than it was.  Now, it
emits nicely reformatted C, an AST as text, and it's emitting
some very rudimentary assembly code, but it has a long, ...
long way to go to properly compile C code.  Fortunately,
I have a number of other simpler C projects.

I also recently made some great progress on my OS-like
environment for DOS that provides a console window for DOS.
It's coded for DJGPP (GCC) C and uses CWSDPMI features.
I now just need to find some use for it.  At the moment it
doesn't provide any advantage over a standard DOS command
line, except I can watch PM interrupts, which are only called
by DJGPP apps, and install PM interrupts and keep them active.
So, no RM interrupts are being monitored at the moment.  The
Windows 98/SE console windows was much faster than DOS.  So,
improving speed is one potential option for a purpose.
Unfortunately, switching RM interrupts back to PM has overhead
which could reduce any real gains from 32-bit PM C code.
Unfortunately, CWSDPMI doesn't use v86, unless VCPI is
installed, which would've reflected all RM interrupts to PM.


Rod Pemberton


-- 
Just how many texting and calendar apps does humanity need?

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C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-11 19:11 -0400
  Re: C parser ramblings, language design, etc "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-12 05:10 -0700
    Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 04:41 -0400
      Re: C parser ramblings, language design, etc "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 02:37 -0700
        Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 07:20 -0400
          Re: C parser ramblings, language design, etc "James Harris" <james.harris.1@gmail.com> - 2015-09-13 18:37 +0100
        Re: C parser ramblings, language design, etc "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 21:03 -0700
  Re: C parser ramblings, language design, etc "James Harris" <james.harris.1@gmail.com> - 2015-09-12 13:49 +0100
    Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 06:27 -0400
      Re: C parser ramblings, language design, etc "James Harris" <james.harris.1@gmail.com> - 2015-09-13 19:02 +0100
        Re: C parser ramblings, language design, etc "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 15:10 -0700
        Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 20:30 -0400
          Re: C parser ramblings, language design, etc "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 20:07 -0700
          Re: C parser ramblings, language design, etc "James Harris" <james.harris.1@gmail.com> - 2015-09-14 22:29 +0100
            Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-20 18:48 -0400
              Re: C parser ramblings, language design, etc "James Harris" <james.harris.1@gmail.com> - 2015-09-22 20:04 +0100
                Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-30 20:32 -0400
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2015-12-27 13:51 +0000
                Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-12-27 17:35 -0500
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-16 17:09 +0000
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-16 14:30 -0500
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-16 21:40 +0000
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-18 07:34 -0500
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-18 08:37 -0500
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-18 23:35 +0000
                Re: C parser ramblings, language design, etc "wolfgang kern" <nowhere@never.at> - 2016-01-19 12:52 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-19 13:09 +0000
                Re: C parser ramblings, language design, etc "wolfgang kern" <nowhere@never.at> - 2016-01-19 21:46 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-21 11:15 +0000
                Re: C parser ramblings, language design, etc "wolfgang kern" <nowhere@never.at> - 2016-01-21 21:48 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-22 15:16 +0000
                Re: C parser ramblings, language design, etc "wolfgang kern" <nowhere@never.at> - 2016-01-22 23:02 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-01-23 17:04 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-27 15:27 +0000
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-02-29 09:26 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-02-29 19:02 +0000
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-03-02 20:48 +0000
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-03-09 22:29 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-03-17 16:41 +0000
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-03-29 09:00 +0200
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-03-09 22:29 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-03-17 17:36 +0000
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-03-29 09:01 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-04-02 10:13 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-04-10 19:33 +0200
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-04-15 16:27 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-04-26 08:10 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-05-03 20:14 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-05-04 09:17 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-05-21 21:10 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-05-29 08:44 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-05-29 12:05 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-05-29 12:28 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-06-01 19:22 +0200
                OT: Obama in the UK (was: C parser ramblings, language design, etc) James Harris <james.harris.1@gmail.com> - 2016-04-26 08:46 +0100
                Re: OT: Obama in the UK (was: C parser ramblings, language design, etc) Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-04-26 23:58 -0400
                Re: OT: Obama in the UK (was: C parser ramblings, language design, etc) Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-04-27 00:08 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-04-27 06:40 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-04-27 05:25 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-04-27 17:45 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-04-27 18:25 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-02 23:44 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-03 16:56 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-04 09:23 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-04 17:22 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-06 11:47 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-06 19:34 -0400
                Re: OT: Obama in the UK "James Harris" <james.harris.1@gmail.com> - 2016-05-07 12:51 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-07 19:20 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-08 01:46 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-07 21:43 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-08 09:36 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-08 15:34 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-10 11:25 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-10 17:32 -0400
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-10 18:25 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-15 00:06 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-07 21:32 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-06-02 07:41 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-06-02 16:21 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-20 14:59 +0100
                Re: OT: Obama in the UK "wolfgang kern" <nowhere@never.at> - 2016-05-20 21:13 +0200
                Re: OT: Obama in the UK "wolfgang kern" <nowhere@never.at> - 2016-05-20 21:17 +0200
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-21 08:04 +0100
                Re: OT: Obama in the UK Bernhard Schornak <schornak@web.de> - 2016-05-21 21:10 +0200
                Re: OT: Obama in the UK "wolfgang kern" <nowhere@never.at> - 2016-05-21 11:16 +0200
                Re: OT: Obama in the UK Bernhard Schornak <schornak@web.de> - 2016-05-21 21:11 +0200
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-05-20 22:51 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-21 07:29 +0100
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-06-02 08:33 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-06-02 16:21 -0400
                UK pronunciation was, [Re: OT: Obama in the UK, was C lang parser ramblings] Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-06-11 14:34 -0400
                Re: UK pronunciation was, [Re: OT: Obama in the UK, was C lang parser ramblings] James Harris <james.harris.1@gmail.com> - 2016-07-24 18:28 +0100
                Re: UK pronunciation was, [Re: OT: Obama in the UK, was C lang parser ramblings] Rod Pemberton <NoHaveNotOne@bcczxcfrze.cam> - 2016-07-25 21:54 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-07-24 18:21 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfrze.cam> - 2016-07-25 21:54 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-07-26 10:02 +0100
                Re: OT: Obama in the UK Rod Pemberton <NoHaveNotOne@bcczxcfrze.cam> - 2016-07-26 07:56 -0400
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-07-30 12:26 +0100
                Re: OT: Obama in the UK Bernhard Schornak <schornak@web.de> - 2016-05-03 20:14 +0200
                Re: OT: Obama in the UK James Harris <james.harris.1@gmail.com> - 2016-05-04 09:25 +0100
                Re: OT: Obama in the UK Bernhard Schornak <schornak@web.de> - 2016-05-21 21:11 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-04-26 07:59 +0100
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-04-27 00:01 -0400
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-04-27 09:28 +0100
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-04-27 05:42 -0400
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-04-27 17:16 +0100
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-04-27 18:05 -0400
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-04-27 09:29 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-04-27 09:42 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-05-03 20:14 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-05-07 14:34 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-05-21 21:10 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-05-29 11:27 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-06-01 19:22 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-05-07 16:34 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-05-21 21:10 +0200
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-05-29 12:10 +0100
                Re: C parser ramblings, language design, etc Bernhard Schornak <schornak@web.de> - 2016-06-01 19:22 +0200
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-25 18:29 -0500
                Re: C parser ramblings, language design, etc "wolfgang kern" <nowhere@never.at> - 2016-01-26 11:47 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-27 17:08 +0000
                Re: C parser ramblings, language design, etc "wolfgang kern" <nowhere@never.at> - 2016-01-28 11:54 +0100
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-28 11:47 +0000
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-21 10:13 +0000
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-25 18:29 -0500
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-27 17:15 +0000
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-27 17:31 -0500
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-28 11:07 +0000
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-19 22:28 -0500
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-22 15:04 +0000
                Re: C parser ramblings, language design, etc Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-25 17:48 -0500
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2016-01-27 17:16 +0000
                Re: cows and bulls game, was [Re: C parser ramblings, language design, etc] "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-12-27 21:19 -0500
              Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-30 20:32 -0400
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2015-10-05 15:13 +0100
                Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-10-05 21:56 -0400
                Re: C parser ramblings, language design, etc James Harris <james.harris.1@gmail.com> - 2015-12-27 13:56 +0000
                Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-10-21 19:46 -0400
  Re: C parser ramblings, language design, etc "James Harris" <james.harris.1@gmail.com> - 2015-09-12 15:38 +0100
    Re: C parser ramblings, language design, etc "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 07:10 -0400
  Re: C parser ramblings, language design, etc "s_dubrovich@yahoo.com" <s_dubrovich@yahoo.com> - 2015-11-01 09:07 -0800

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