private SpelNode EatSumExpression()
{
var expr = EatProductExpression();
while (PeekToken(TokenKind.PLUS, TokenKind.MINUS, TokenKind.INC))
{
// consume PLUS or MINUS or INC
var t = TakeToken();
var rhExpr = EatProductExpression();
CheckRightOperand(t, rhExpr);
if (t.Kind == TokenKind.PLUS)
{
expr = new OpPlus(t.StartPos, t.EndPos, expr, rhExpr);
}
else if (t.Kind == TokenKind.MINUS)
{
expr = new OpMinus(t.StartPos, t.EndPos, expr, rhExpr);
}
}
return(expr);
}
public static Expr _UnaryMinus(OpMinus op, Expr rhs)
{
return(new UnaryMinusExpr(rhs));
}
public static Expr _Sub(Expr lhs, OpMinus op, Expr rhs)
{
return(new SubExpr(lhs, rhs));
}