Looking for good table with all Java operators
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From: Roedy Green on 25 Jan 2010 11:51 On Mon, 25 Jan 2010 14:00:36 +0100, "Robbo" <nie.mam(a)yle.com> wrote, quoted or indirectly quoted someone who said : >There is no information about "new" which is also operator: new does behave like an ordinary operator with precedence. It must be immediately followed by a ClassName. It cannot occur in any other context. I guess one way of looking at this is new has extremely high precedence. It is in my table. see http://mindprod.com/jgloss/precedence.html My table also has some notes on each operator, MORE button links to a detailed discussion of each operator, and examples of use. My table is aimed at newbies, not language lawyers (compiler implementors). I still need to write something on == and !=, and the += family. -- Roedy Green Canadian Mind Products http://mindprod.com Don�t be discouraged by a failure. It can be a positive experience. Failure is, in a sense, the highway to success, inasmuch as every discovery of what is false leads us to seek earnestly after what is true, and every fresh experience points out some form of error which we shall afterwards carefully avoid. ~ John Keats (born: 1795-10-31 died: 1821-02-23 at age: 25)
From: Robbo on 25 Jan 2010 15:31 > see http://mindprod.com/jgloss/precedence.html Your table is good piece of work. Much better than many incomplete tutorials which may be found all over the internet. But, if I am right, a few hours ago there was no information about "new". Probably you have added it not more than a few hours ago. Where did you find information that "new" is officially operator in Java? I am really interested in this topic. Patricia Shanahan (in this thread) has said that "new" is not an operator. I have not found any information that would confirm that "new" is an operator in JLS (3rd edition). And the second thing. In your table there is (cast) operator at precedence of 1 (it has the same priority as prefix and unary operators). Also association is "Right". If I am right (byte)++x means that ++ is computed before (byte) -- both (cast) and prefix ++ have the same priority and association is "Right". And in (byte)x++, (byte) is first because of higher priority of cast than postfix ++. What do you think? Robbo
From: Mike Schilling on 25 Jan 2010 15:55 Robbo wrote: >> see http://mindprod.com/jgloss/precedence.html > > Your table is good piece of work. Much better than many > incomplete tutorials which may be found all over the internet. > > But, if I am right, a few hours ago there was no information > about "new". Probably you have added it not more than > a few hours ago. > Where did you find information that "new" is officially > operator in Java? I am really interested in this topic. > Patricia Shanahan (in this thread) has said that "new" is not an > operator. I have not found any information that would confirm > that "new" is an operator in JLS (3rd edition). "Operator" means different things to different people. A parser guy would probably call "new" an operator; because it combines expressions into a more complex expression and has a defined precedence. But the "offical" list of operators is found at http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#3.12 and doesn't include cast, new, or parentheses. > And the second thing. In your table there is (cast) operator > at precedence of 1 (it has the same priority as prefix and unary > operators). Also association is "Right". > If I am right (byte)++x means that ++ is computed before (byte) > -- both (cast) and prefix ++ have the same priority and association > is "Right". > And in (byte)x++, (byte) is first because of higher priority of > cast > than postfix ++. > What do you think? Other way around. Postfix ++ has a higher precedence than the cast does.
From: Robbo on 25 Jan 2010 16:34 > Other way around. Postfix ++ has a higher precedence than the cast > does. It means there is mistake in Mr. Doedy Green's table (http://mindprod.com/jgloss/precedence.html). In this table prefix and postfix has the same priority -- probably simple mistake with numbers of precedence. But more serious mistake in his table is that prefix is before postfix. According to http://java.sun.com/docs/books/tutorial/java/nutsandbolts/operators.html postfix goes first. I really wish official table of Java operators with precedence and associations. In C++ situations is not better. E.g. here http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B there is information that postfix has precedence 2 and prefix has precedence 3. In my Polish edition of Stroustrup's book postfix and prefix has the same precedence. Robbo
From: Lew on 25 Jan 2010 17:06
Robbo wrote: >> Your table is good piece of work. Much better than many >> incomplete tutorials which may be found all over the internet. >> >> But, if I am right, a few hours ago there was no information >> about "new". Probably you have added it not more than >> a few hours ago. >> Where did you find information that "new" is officially >> operator in Java? I am really interested in this topic. > It is not. The keyword 'new' is officially not an operator in Java. > > Patricia Shanahan (in this thread) has said that "new" is not an > > operator. I have not found any information that would confirm > > that "new" is an operator in JLS (3rd edition). > That's because 'new' is not an operator in the JLS (any edition), ergo in the Java language. As Patricia also pointed out, the JLS defines the language, therefore there is no higher authority. Mike Schilling wrote: > "Operator" means different things to different people. A parser guy > would probably call "new" an operator; because it combines expressions > into a more complex expression and has a defined precedence. But the > "offical" list of operators is found at > <http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#3.12> > This link has been posted before in this thread. OP: you should read it. > and doesn't include cast, new, or parentheses. > nor "dot". However, the JLS does refer to 'instanceof' as an operator. This question has now been answered several times in this thread. You might want to consider accepting the answer. Robbo wrote: >> And the second thing. In your table there is (cast) operator >> at precedence of 1 (it has the same priority as prefix and unary >> operators). Also association is "Right". Don't you mean "associativity"? >> If I am right (byte)++x means that ++ is computed before (byte) >> -- both (cast) and prefix ++ have the same priority and association [sic] >> is "Right". >> And in (byte)x++, (byte) is first because of higher priority of >> cast than postfix ++. >> What do you think? > Mike Schilling wrote: > Other way around. Postfix ++ has a higher precedence than the cast > does. I believe the issue here is one of associativity, not precedence. Both cast and postfix operators are right-associative, therefore the postfix operator is evaluated first. The precedence is indicated by the order in which the operators and other expressions (e.g., cast expressions) appear in chapter 15 of the JLS. <http://java.sun.com/docs/books/jls/third_edition/html/j3TOC.html> and is defined by the productions in <http://java.sun.com/docs/books/jls/third_edition/html/ syntax.html#18.1> -- Lew |