identifier

I stumbled on some C++ code like this: int $T$S; First I thought that it was some sort of PHP code or something wrongly pasted in there but it compiles and runs nicely (on MSVC 2008). What kind of characters are valid for variables in C++ and are there any other weird characters you can use? The only legal characters according to the standard are alphanumerics and the underscore. The standard does require that just about anything Unicode considers alphabetic is acceptable (but only as single code-point characters). In practice, implementations offer extensions (i.e. some do accept a $) and

Recently started digging in to JSON, and I'm currently trying to use a number as "identifier", which doesn't work out too well. foo:"bar" works fine, while 0:"bar" doesn't. var Game = { status: [ { 0:"val", 1:"val", 2:"val" }, { 0:"val", 1:"val", 2:"val" } ] } alert(Game.status[0].0); Is there any way to do it the following way? Something like Game.status[0].0 Would make my life way easier. Of course there's other ways around it, but this way is preferred. JSON only allows key names to be strings. Those strings can consist of numerical values. You aren't using JSON though. You have a

Take this simple data frame of linked ids: test <- data.frame(id1=c(10,10,1,1,24,8),id2=c(1,36,24,45,300,11)) > test id1 id2 1 10 1 2 10 36 3 1 24 4 1 45 5 24 300 6 8 11 I now want to group together all the ids which link. By 'link', I mean follow through the chain of links so that all ids in one group are labelled together. A kind of branching structure. i.e: Group 1 10 --> 1, 1 --> (24,45) 24 --> 300 300 --> NULL 45 --> NULL 10 --> 36, 36 --> NULL, Final group members: 10,1,24,36,45,300 Group 2 8 --> 11 11 --> NULL Final group members: 8,11 Now I roughly know the logic I would want, but don

I am reading for SCJP and I have a question regarding this line: Identifiers must start with a letter, a currency character ($), or a connecting character such as the underscore ( _ ). Identifiers cannot start with a number! It states that a valid identifier name can start with a connecting character such as underscore. I thought underscores were the only valid option? What other connecting characters are there? Peter Lawrey Here is a list of connecting characters. These are characters used to connect words. http://www.fileformat.info/info/unicode/category/Pc/list.htm U+005F _ LOW LINE U+203F