/// <summary>
/// An EXPR is normally just a string literal, but is still an AST that
/// we must evaluate. The EXPR can be any expression such as a template
/// include or string cat expression etc...
///
/// Evaluate with its own writer so that we can convert to string and then
/// reuse, don't want to compute all the time; must precompute w/o writing
/// to output buffer.
/// </summary>
protected internal string EvaluateExpression(StringTemplate self, object expr)
{
if (expr == null)
{
return null;
}
if (expr is StringTemplateAST)
{
StringTemplateAST exprTree = (StringTemplateAST) expr;
// must evaluate, writing to a string so we can hand on to it
StringWriter buf = new StringWriter();
IStringTemplateWriter sw = self.group.CreateInstanceOfTemplateWriter(buf);
ActionEvaluator eval = new ActionEvaluator(self, this, sw);
try
{
eval.action(exprTree); // eval tree
}
catch (RecognitionException ex)
{
self.Error("can't evaluate tree: " + exprTree.ToStringList(), ex);
}
return buf.ToString();
}
else
{
// just in case we expand in the future and it's something else
return expr.ToString();
}
}
/// <summary>
/// To write out the value of an ASTExpr, invoke the evaluator in eval.g
/// to walk the tree writing out the values. For efficiency, don't
/// compute a bunch of strings and then pack them together. Write out directly.
///
/// Compute separator and wrap expressions, save as strings so we don't
/// recompute for each value in a multi-valued attribute or expression.
///
/// If they set anchor option, then inform the writer to push current
/// char position.
/// </summary>
public override int Write(StringTemplate self, IStringTemplateWriter output)
{
if (exprTree == null || self == null || output == null)
{
return 0;
}
output.PushIndentation(Indentation);
// handle options, anchor, wrap, separator...
StringTemplateAST anchorAST = (StringTemplateAST)GetOption("anchor");
if (anchorAST != null) // any non-empty expr means true; check presence
{
output.PushAnchorPoint();
}
HandleExprOptions(self);
ActionEvaluator eval = new ActionEvaluator(self, this, output);
ActionParser.initializeASTFactory(eval.getASTFactory());
int n = 0;
try
{
n = eval.action(exprTree); // eval and write out tree
}
catch (RecognitionException re)
{
self.Error("can't evaluate tree: " + exprTree.ToStringList(), re);
}
output.PopIndentation();
if (anchorAST != null)
{
output.PopAnchorPoint();
}
return n;
}