public override void Visit(BinaryOpNode node)
{
Contracts.AssertValue(node);
if (TryShowValue(node))
{
return;
}
Precedence prec = GetPrec(node.Op);
Precedence prec1 = GetPrec(node.Left);
Precedence prec2 = GetPrec(node.Right);
bool parens1 = NeedParensLeft(prec1, prec);
bool parens2 = NeedParensRight(prec, prec2);
if (parens1)
{
_wrt.Write('(');
}
node.Left.Accept(this);
if (parens1)
{
_wrt.Write(')');
}
_wrt.Write(GetString(node.Op));
if (parens2)
{
_wrt.Write('(');
}
node.Right.Accept(this);
if (parens2)
{
_wrt.Write(')');
}
ShowType(node);
}
// Parses the next (maximal) expression with precedence >= precMin.
private ExprNode ParseExpr(Precedence precMin)
{
// ParseOperand may accept PrefixUnary and higher, so ParseExpr should never be called
// with precMin > Precedence.PrefixUnary - it will not correctly handle those cases.
Contracts.Assert(Precedence.None <= precMin);
Contracts.Assert(precMin <= Precedence.PrefixUnary);
// Get the left operand.
ExprNode node = ParsePrimary();
// Process operators and right operands as long as the precedence bound is satisfied.
for (; ;)
{
Contracts.AssertValue(node);
switch (TidCur)
{
case TokKind.Car:
Contracts.Assert(precMin <= Precedence.Power);
// Note that the right operand can include unary operators.
node = new BinaryOpNode(TokMove(), BinaryOp.Power, node, ParseExpr(Precedence.PrefixUnary));
break;
case TokKind.Mul:
if (precMin > Precedence.Mul)
{
return(node);
}
node = new BinaryOpNode(TokMove(), BinaryOp.Mul, node, ParseExpr(Precedence.Mul + 1));
break;
case TokKind.Div:
if (precMin > Precedence.Mul)
{
return(node);
}
node = new BinaryOpNode(TokMove(), BinaryOp.Div, node, ParseExpr(Precedence.Mul + 1));
break;
case TokKind.Per:
if (precMin > Precedence.Mul)
{
return(node);
}
node = new BinaryOpNode(TokMove(), BinaryOp.Mod, node, ParseExpr(Precedence.Mul + 1));
break;
case TokKind.Sub:
if (precMin > Precedence.Add)
{
return(node);
}
node = new BinaryOpNode(TokMove(), BinaryOp.Sub, node, ParseExpr(Precedence.Add + 1));
break;
case TokKind.Add:
if (precMin > Precedence.Add)
{
return(node);
}
node = new BinaryOpNode(TokMove(), BinaryOp.Add, node, ParseExpr(Precedence.Add + 1));
break;
case TokKind.AmpAmp:
case TokKind.And:
if (precMin > Precedence.And)
{
return(node);
}
node = new BinaryOpNode(TokMove(), BinaryOp.And, node, ParseExpr(Precedence.And + 1));
break;
case TokKind.BarBar:
case TokKind.Or:
if (precMin > Precedence.Or)
{
return(node);
}
node = new BinaryOpNode(TokMove(), BinaryOp.Or, node, ParseExpr(Precedence.Or + 1));
break;
case TokKind.QueQue:
if (precMin > Precedence.Coalesce)
{
return(node);
}
// Note that the associativity is different than other binary operators (right instead of left),
// so the recursive call accepts Precedence.Coal.
node = new BinaryOpNode(TokMove(), BinaryOp.Coalesce, node, ParseExpr(Precedence.Coalesce));
break;
case TokKind.Que:
if (precMin > Precedence.Conditional)
{
return(node);
}
node = new ConditionalNode(TokMove(), node, ParseExpr(), TokEat(TokKind.Colon), ParseExpr());
break;
// Comparison operators
// expr = ... = expr
// expr <> ... <> expr
case TokKind.Equ:
case TokKind.EquEqu:
if (precMin > Precedence.Compare)
{
return(node);
}
node = ParseCompareExpr(node, CompareOp.Equal, TokKind.Equ, TokKind.EquEqu);
break;
case TokKind.LssGrt:
case TokKind.BngEqu:
if (precMin > Precedence.Compare)
{
return(node);
}
node = ParseCompareExpr(node, CompareOp.NotEqual, TokKind.LssGrt, TokKind.BngEqu);
break;
// expr < expr
// expr <= expr
case TokKind.Lss:
case TokKind.LssEqu:
if (precMin > Precedence.Compare)
{
return(node);
}
node = ParseCompareExpr(node, CompareOp.IncrChain, TokKind.LssEqu, TokKind.Lss);
break;
// expr > expr
// expr >= expr
case TokKind.Grt:
case TokKind.GrtEqu:
if (precMin > Precedence.Compare)
{
return(node);
}
node = ParseCompareExpr(node, CompareOp.DecrChain, TokKind.GrtEqu, TokKind.Grt);
break;
case TokKind.True:
case TokKind.False:
case TokKind.IntLit:
case TokKind.FltLit:
case TokKind.DblLit:
case TokKind.CharLit:
case TokKind.StrLit:
PostError(TokCur, "Operator expected");
node = new BinaryOpNode(TokCur, BinaryOp.Error, node, ParseExpr(Precedence.Error));
break;
default:
return(node);
}
}
}
public override void PostVisit(BinaryOpNode node)
{
Contracts.Assert(false);
}
public override bool PreVisit(BinaryOpNode node)
{
Visit(node); return(false);
}
public abstract void Visit(BinaryOpNode node);
public virtual bool PreVisit(BinaryOpNode node)
{
return(true);
}