# file: GeneratorE.eyp
# compile with: eyapp -C '' GeneratorE.eyp
# then run: ./GeneratorE.pm
%strict
%token NUM VARDEF VAR

%right  '='
%left   '-' '+'
%left   '*' '/'
%right  '^'

%defaultaction {
  my $parser = shift;

  return join '', @_;
}

%{
use base q{Parse::Eyapp::TokenGen};
%}

%%

stmts:
    stmt
      {
        $_[0]->deltaweight(VAR => +2); # At least one variable is defined now
        $_[1];
      }
  | stmts ';' { "\n" } stmt 
;

stmt:
    $VARDEF '=' $exp  
      {
        my $parser = shift;

        my $res = EVALUATE($exp);
        return '' if $res =~ /^error/;

        $parser->defined_variable($VARDEF, $exp, $res); 

        "$VARDEF=$exp";
      }
;
exp:
    NUM                
  | VAR
  | exp '+' exp        
  | exp '-' exp        
  | exp '*' exp        
  | exp '/' exp        
  | exp '^' exp        
  | '('   { $_[0]->pushdeltaweight('(' => -1, ')' => +1, '+' => +1, ); } 
      exp 
    ')'
      {
         $_[0]->popweight; 
         "($_[3])"
      }
;

%%

my $prefix = "no warnings; no strict;\n";

use Getopt::Long;
use Test::LectroTest::Generator qw(:all);

my %st; # Symbol Table
sub defined_variable {
  my ($parser, $var, $exp, $value) = @_;

  $st{$var} = { exp => $exp, value => $value};
  $prefix .= '$'."$var = $value;\n";
}

sub EVALUATE { # if possible
  my $perlexp = shift;

  $perlexp =~ s/\b([a-zA-Z])/\$$1/g; # substitute A by $A everywhere 
  $perlexp =~ s/\^/**/g;             # substitute power operator: ^ by **

  my $program = "$prefix$perlexp";
  #print "***program***\n$program\n****\n";
  my $res = eval $program;
  if ($@) {
    $@ =~ m{(.{1,10})}; 
    $res = "error. $1"; 
  }

  $res;
}


use Data::Dumper;
sub main {
  my $package = shift;

  my $debug = shift || 0;
  my $numtimes = shift || 1;
  my $result = GetOptions (
    "debug!" => \$debug,  
    "times=i" => \$numtimes,  
  );

  $debug = 0x1F if $debug;

  # LexerGen receives the parser object and the pairs 
  #   token => [weight, generator] or token => weight
  # and returns a generator subroutine
  my $gen = $package->new(); 
  $gen->LexerGen(
          NUM => [ 2, Int(range=>[0, 9], sized=>0)],
          VAR => [
                    0,  # At the beginning, no variables are defined
                    Gen {
                      return  Elements(keys %st)->generate if keys %st;
                      return Int(range=>[0, 9], sized=>0)->generate;
                    },
                  ],
          VARDEF => [ 
                      2,  
                      String( length=>[1,2], charset=>"A-NP-Z", size => 100 )
                    ],
          '=' => 2, '-' => 1, '+' => 2, 
          '*' => 4, '/' => 2, '^' => 0.5, 
          ';' => 3, '(' => 1, ')' => 2, 
          ''  => 2, 'error' => 0,
  );
  for (1..$numtimes) {
    my $exp = $gen->generate( 
        yydebug => $debug, # 0x1F
      );

    my $res = EVALUATE($exp);

    print "\n# result: $res\n$exp\n";
    #print "$_ = ".Dumper($st{$_})."\n" for keys(%st);
  }
}