%token NUM = /(\d+)/
%token OP  = /([-+*\/])/

%{
my $nxr = 0;
my $nxs = 0;
%}

%conflict isInTheMiddle {

  $nxs++;

  if ($nxs == $nxr+1) { 
    print "Reducing by :MIDx input = '".unexpendedInput()."'\n";
    $self->YYSetReduce(['NUM', 'OP', ';' ], ':MIDx' );
    
    $nxr = $nxs = 0; 
  }
  else { $self->YYSetShift('NUM') } 
}  

%explorer isInTheMiddle {
   ($nxr) = $self->YYPreParse('ExpList'); 
   print "Number of x's = $nxr\n";
   $nxr = int ($nxr/2);
}

%%

T: %isInTheMiddle? S ';' %isInTheMiddle? S ';'
;

S:
     x  %PREC isInTheMiddle S x  
  |  %name :MIDx 
     x  %PREC isInTheMiddle 
;

x:
     NUM
  |  NUM OP x
;
%%

=head1 SYNOPSIS

This grammar is similar to the one in file C<nopackrat.eyp>.
It can't be parsed by LR(k) nor LL(k) algorithms.
Backtracking LR and GLR algorithms can but will perform poorly.

Compile it with:

   $ eyapp -P ExpList.eyp 
   $ eyapp -TC noPackratSolvedExpRGconcept.eyp

Run it with:

   $ ./noPackratSolvedExpRGconcept.pm -t -i -m 1 -c '2; 1 2+2 3-5;'

=head1 SEE ALSO

Files C<nopackrat.eyp>, C<noLRk_exp.eyp>, C<noLRk_expSolved.eyp>

=cut