Generating C++ code from an SPL expression tree

An SPL expression tree represents the SPL expression for a parameter or output expression in a form that can be easily traversed in a C++ primitive operator. To use SPL expression trees, the context of the primitive operator must include an <splExpressionTree [param="true|false"] [output="true|false"] [cppCode="true|false"]/> element.

Each node in an SPL expression tree can be examined to determine the SPL type, the expression kind, and the C++ code for the node (if cppCode="true" is specified). For each expression kind, the associated information can be returned. An example is the right side and left side expressions for a binary operator, or the identifier in an identifier expression.

A subclass of ExpressionTreeVisitor (ExpressionTreeCppGenVisitor) is provided to walk the SPL expression tree and use the cppCode fields to regenerate the C++ code. To use ExpressionTreeCppGenVisitor, the SPL expression tree must be created with <splExpressionTreeMode cppCode="true"> in the operator model for the primitive operator. This code causes the generated C++ code for the SPL expression to be placed in the SPL expression tree in a form that can be used to generate code.

my $g = SPL::Operator::Instance::ExpressionTreeCppGenVisitor->new();
$g->visit ($expn->getSPLExpressionTree())
my $cppCode = $g->getCppCode();
# $cppCode contains a C++ expression that will evaluate to the expression.

package Gen;
use base qw(SPL::Operator::Instance::ExpressionTreeCppGenVisitor);
sub visit_CallExpression($$)
{
    my ($self, $expn) = @_;
    my $fcnName = $expn->getFunctionName();
    if ($fcnName =~ /^MatchRegex::(.*)/) {
        $fcnName = $1;
        if ($fcnName eq 'Count') {
            $self->append('(CEP$COUNT+pmatch._Count)');
        } elsif ($fcnName eq "Any") {
            		# gen different code here
	 }
    	return;
    }

   $self->SUPER::visit_CallExpression($expn);
}

my $subExpn = $self->new();
$subExpn->visit($a);
$self->append($subExpn->getCppCode());