public static string PrintExpr(AstExpr astRoot)
{
switch (astRoot.m_exprk)
{
case EXPRK.Binary:
{
AstBinaryExpr expr = (AstBinaryExpr)astRoot;
return("( " + expr.m_tokenkOp.ToString() + " " + PrintExpr(expr.m_leftExpr) + " " + PrintExpr(expr.m_rightExpr) + " )");
} break;
case EXPRK.Group:
{
AstGroupExpr group = (AstGroupExpr)astRoot;
return("( " + PrintExpr(group.m_expr) + " )");
} break;
case EXPRK.Literal:
{
AstLiteralExpr expr = (AstLiteralExpr)astRoot;
return(expr.m_value.ToString());
} break;
case EXPRK.Unary:
{
AstUnaryExpr expr = (AstUnaryExpr)astRoot;
return("( " + expr.m_tokenkOp.ToString() + " " + PrintExpr(expr.m_expr) + " )");
} break;
default:
{
Debug.Fail("Print not implemented for Ast Node type: " + astRoot.m_astnodek);
return("<error>");
} break;
}
}
protected object EvaluateUnaryExpr(AstUnaryExpr expr)
{
if (HadErrorOrReturn())
{
return(null);
}
object value = EvaluateExpr(expr.m_expr);
switch (expr.m_tokenkOp)
{
case TOKENK.Bang:
{
return(!IsTruthy(value));
} break;
case TOKENK.Minus:
{
double?numVal = value as double?;
if (numVal.HasValue)
{
return(-numVal.Value);
}
m_runtimeError = true;
Lox.Error(expr.m_startLine, "Unary - operator can only be applied to numbers");
} break;
default:
{
m_runtimeError = true;
Lox.InternalError(expr.m_startLine, "Unary expression has unexpected operator: " + expr.m_tokenkOp);
} break;
}
Debug.Assert(m_runtimeError);
return(null);
}
public virtual ReturnType VisitUnaryExpr(AstUnaryExpr expr, DataType data = default) => default;
protected void ResolveUnaryExpr(AstUnaryExpr expr)
{
ResolveExpr(expr.m_expr);
}
public override string VisitUnaryExpr(AstUnaryExpr bin, int data = 0)
{
var sub = bin.SubExpr.Accept(this, 0);
return(bin.Operator + sub);
}