public Expr OnParseIf()
{
var tokenIt = this._parser.TokenIt;
var initiatorToken = tokenIt.NextToken;
var expr = new IfExpr();
// <codeIf>
tokenIt.Expect(Tokens.If);
// Parse the if
this.ParseConditionalBlock(expr);
tokenIt.AdvancePastNewLines();
// Handle "else if" and/or else
if (tokenIt.NextToken.Token == Tokens.Else)
{
// tokenIt.NextToken = "else"
tokenIt.Advance();
tokenIt.AdvancePastNewLines();
// What's after else?
// 1. "if" = else if statement
// 2. "{" = multi line else
// 3. "nothing" = single line else
// Peek 2nd token for else if.
var token = tokenIt.NextToken;
if (tokenIt.NextToken.Token == Tokens.If)
{
expr.Else = OnParseIf() as BlockExpr;
}
else // Multi-line or single line else
{
var elseStmt = new BlockExpr();
this._parser.ParseBlock(elseStmt);
this._parser.SetupContext(elseStmt, token);
expr.Else = elseStmt;
}
}
// </codeIf>
this._parser.SetupContext(expr, initiatorToken);
return expr;
}
/// <summary>
/// Execute
/// </summary>
public object VisitIf(IfExpr expr)
{
// Case 1: If is true
var result = expr.Condition.Evaluate(this) as LObject;
bool execIf = EvalHelper.IsTrue(result);
object returnVal = LObjects.Null;
if (execIf)
{
if (expr.Statements != null && expr.Statements.Count > 0)
{
foreach (var stmt in expr.Statements)
{
returnVal = stmt.Evaluate(this);
}
}
}
// Case 2: Else available to execute
else if (expr.Else != null)
{
returnVal = expr.Else.Evaluate(this);
}
return returnVal;
}
/// <summary>
/// Visits the if statement tree.
/// </summary>
/// <param name="ifExpr"></param>
public object VisitIf(IfExpr expr)
{
_callBackOnNodeStart(expr);
expr.Condition.Visit(this);
foreach (var stmt in expr.Statements)
{
stmt.Visit(this);
}
if (expr.Else != null)
expr.Else.Visit(this);
return null;
}