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After getting pretty far along with To model or not to model, I've decided that making the application general enough to meet the requirements requires a change to a parsed-grammar approach. I've rewritten almost everything as a Parse::RecDescent grammar.

Almost everything works correctly.

In one case, however, I get strange results back from the @item array, like this:

19|ifthenelse|>>Matched action<< (return value: []) |
19|ifthenelse|>>Matched production: [if elsif else  |
  |          |endif]<<                              |
19|ifthenelse|>>Matched rule<< (return value:       |
  |          |[ARRAY(0x870cb08)])                   |
19|ifthenelse|(consumed: [])                        |
[download]

from source text:

if stw!=0 then stw else 1.40 * 1e-6  endif
[download]

and the following (simplified) grammar:

expr: ifthenelse
      { $return = main::evaluate($main::c_v, @item); }
ifthenelse: if elsif(s?) else(?) endif
        { 
        $return = 'NIL';
        for (my $i = 1; $i < @item; $i++)
        {
          print " iftest: $i '" . $item[$i] . "'\n";
               if ($item[$i] ne 'NIL') { $return = $item[$i]; last; }
        }
        if ($return eq 'NIL')
        { die "IF statement '@item' not resolvable! $!\n"; }
            } 

if:             /if/i expr /then/i expr        
        { print 'i2: ' . $item[2] ."\n"; 
          if($item[2]) { $return = $item[4]; } else { $return = 'NIL';
+ } }

else:           /else/i expr
        { $return = $item[2]; }

elsif:          /elsif/i expr /then/i expr
        { if ($item[2]) { $return = $item[4] } else { $return = 'NIL' 
+} }

endif:          /endif/i { $return = 'NIL'; }
[download]

and main 'engine' subroutine:

sub evaluate
{
    my $contvar = shift;
    shift;
    my $estr = join(' ', @_);
    my @whatsleft = @_;
    print " evaluating '$estr'\n";
    $estr =~ s/ARRAY\x28[^\x28\x29]+\x29//g;
    $estr = trim($estr);
    if ($estr !~ /^[\s\.\/\x28\x290-9eE*+-]+$/)
    {
    my $parser = SpiceGrammar->new()
        or die "Bad SpiceGrammar: $!\n";
    print "  evaluating variable\n";
    defined(my $value = $parser->vardef($estr))
        or die "Bad input: {$estr} $!\n";
    if ($value eq '') { $value = 0; print " substituting\n"; }
    return $value;
    }
    else
    {
    my $value = eval($estr);
    $vartable{$contvar} = $value;
    return $value;
    }
}
[download]

WHen the ELSE clause matched, it (apparently) saved the result properly:


21|   expr   |>>Matched action<< (return value:     |
  |          |[1.4e-06])                            |
21|   expr   |>>Matched production: [number operator|
  |          |expr]<<                               |
21|   expr   |>>Matched rule<< (return value: [1.4e-|
  |          |06])                                  |
21|   expr   |(consumed: [ 1.40 * 1e-6])            |
20|   else   |>>Matched subrule: [expr]<< (return   |
  |          |value: [1.4e-06]                      |
20|   else   |Trying action                         |
20|   else   |>>Matched action<< (return value:     |
  |          |[1.4e-06])                            |
20|   else   |>>Matched production: [/else/i expr]<<|
20|   else   |>>Matched rule<< (return value: [1.4e-|
  |          |06])                                  |
20|   else   |(consumed: [ else 1.40 * 1e-6])       |
19|ifthenelse|>>Matched repeated subrule: [else]<<  |
  |          |(1 times)
[download]

but I can't see where it's going south and returning an array (or the string expression of an array). In other similar cases (outside the ifthenelse-decoder) sub-expression results are returned properly.

TIA for pointers or assistance! :D

In reply to To make the Model WORK by samizdat

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