i thought about providing code, but figured it'd be considerably more than most would care to wade. ok, you asked for it. :-) here's the synopsis: blank lines are erroneously flagged as errors in the precomiled version and the resync seems to cause skipped lines -- see the first instruction is skipped in the .pm case. (notes (1) the grammar keeps track of its successes and prints that as hints in case of failure; (2) the hardware repeat is 1 more than value coded into instruction, so the assembler decrements user provided value.)

correct output from fully interpreted version:

                             1: // test cases.



                             2: 



                             3: // repeat instruction



                             4: 


[0000]  000000f70000

                             5: repeat = 0x0001;



                             6: repeat = 0x0002;


[0001]  000000f70001

                             7: repeat = 0xfade;


[0002]  000000f7fadd
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incorrect output from same input when using precompiled grammar:

                             1: // test cases.



                             2: 




INVALID INSTRUCTION DETECTED.

I got as far as finding ...i had just started!
   (going for anything i might recognise)

my last success ended at LINE 1 COL 1.
You might have a look at that
   last line, or at this line:

                             3: // repeat instruction


skip 1 address, try to continue...


                             3: // repeat instruction



                             4: 



                             5: repeat = 0x0001;



                             6: repeat = 0x0002;


[0001]  000000f70001

                             7: repeat = 0xfade;


[0002]  000000f7fadd
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at a high level, here is the bare bones of the code. first is the interpreted version, later is as changed for use with the precompiled grammar as a .pm file:

#interp'd
$mach_grammar = q
{
[...grammar_contents...]
}
main
{
my $mach_parser = new Parse::RecDescent ($mach_grammar);
#[...]
defined $ns85_parser->program_body($src_code) or die "bad grammar!";
}
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ok, that was the interpreted, now for the precompiled:

#precompiled
use mach_grammar;

main
{
my $mach_parser = mach_grammar->new(); 
#[...]
defined $mach_parser->program_body($src_code) or die "bad grammar!";
}
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in more detail, below is substantially more of the code. the changes are, as noted, very small and a lot harder to see in it all. first is the interpreted version, later is as changed for use with the precompiled grammar as a .pm file. the debug option has been set in each case, so that internal test data is used and the input file (spec'd on the command line) is ignored.

#interp'd
require "/usr/lib/perl5/5.6.1/getopts.pl";
#[...]
our @prog_src;
our $src_code;

our $opt_i;
use vars qw($opt_l);    # L is used in actions inside the grammar

# the machine has 48 bit instruction words, which are built up
#   in two halves.
use vars qw($Instruction_upper);
use vars qw($Instruction_lower);
use vars qw($Instruction_address);

use vars qw($LastPrintedLine);
use vars qw($LineToPrint);

use vars qw($LastSuccess);
use vars qw($LookingFor);
#[...]
$mach_grammar = q
{
program_body :    instruction(s) program_body
            { $return = 1; }
    |    instruction
            { $return = 1; }
    |    end_of_input
            {
                print sprintf "\nend of source at LINE %d\n",
                    $thisline;
                exit;
            }
    |    bad_instr :    {
            print sprintf "\nINVALID INSTRUCTION DETECTED.";
            print sprintf "\n\n%s %s\n   (%s %s)\n",
                "I got as far as finding", $main::LastSuccess,
                "going for", $main::LookingFor;
            $main::Instruction_address += 1;
            print sprintf "\nmy last success ended at LINE %d COL %d."
+,
                $thisline, $thiscolumn;
            print sprintf "\nYou might have a look at that";
            print sprintf "\n   last line, or at this line:";
            print "\n\n                             ";
            print sprintf "%d: %s",
                $main::LastPrintedLine + 2,
                @main::prog_src[$main::LastPrintedLine+1];
            print sprintf "\nskip 1 address, try to continue...\n";
        }
        <resync:[^;]*[;]>


#[....major snippage...]

hexval :    /0x[0-9A-F]+/i
            {
                $return = hex $item[1];
                1;
            }


};
# end of grammar
#
# main program follows
#
{
my $mach_parser = new Parse::RecDescent ($mach_grammar);
#[...]
# acquire @prog_src
if ($debug == 1)
{
    @prog_src = <DATA> or die "ERROR: cannot read input data.";
} else
{
# open the input file
    open(INFILE, "$opt_i") || die "ERROR: Cannot open $opt_i";
    @prog_src = <INFILE> or die "ERROR: cannot read input file.";
    close(INFILE);
}
#
# mash all the source together and remove all the newlines.
#

foreach (0 .. scalar(@prog_src) - 1)
{
    $prog_src[@_] =~ s/\\r/\$\//g ;
}


push @prog_src, "\n__EOF__";

$src_code = join " ", @prog_src;

defined $mach_parser->program_body($src_code) or die "bad grammar!";

}
#
# ******************************************************************
# main program section has ended, debug data section follows.
# ******************************************************************
#

__DATA__
// test cases.

// repeat instruction

repeat = 0x0001;
repeat = 0x0002;
repeat = 0xfade;

//[...rest of test cases removed...]

/* that's all folks.... */

__EOF__
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and the precompiled usage has the grammar all off in another file, precompiled to mach_grammar.pm and the main code then looks like:

require "/usr/lib/perl5/5.6.1/getopts.pl";
#[...]
use mach_grammar;
our @prog_src;
our $src_code;

our $opt_i;
use vars qw($opt_l);    # L is used in actions inside the grammar

# the machine has 48 bit instruction words, which are built up
#   in two halves.
use vars qw($Instruction_upper);
use vars qw($Instruction_lower);
use vars qw($Instruction_address);

use vars qw($LastPrintedLine);
use vars qw($LineToPrint);

use vars qw($LastSuccess);
use vars qw($LookingFor);
#
# main program follows
#
{
my $mach_parser = mach_grammar->new(); 
#[...]
# acquire @prog_src
if ($debug == 1)
{
    @prog_src = <DATA> or die "ERROR: cannot read input data.";
} else
{
# open the input file
    open(INFILE, "$opt_i") || die "ERROR: Cannot open $opt_i";
    @prog_src = <INFILE> or die "ERROR: cannot read input file.";
    close(INFILE);
}
#
# mash all the source together and remove all the newlines.
#

foreach (0 .. scalar(@prog_src) - 1)
{
    $prog_src[@_] =~ s/\\r/\$\//g ;
}

push @prog_src, "\n__EOF__";

$src_code = join " ", @prog_src;

defined $mach_parser->program_body($src_code) or die "bad grammar!";
}
#
# ******************************************************************
# main program section has ended, debug data section follows.
# ******************************************************************
#

__DATA__
// test cases.

// repeat instruction

repeat = 0x0001;
repeat = 0x0002;
repeat = 0xfade;

//[...rest of test cases removed...]

/* that's all folks.... */

__EOF__
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