We published JCR -06 back in March and since we’ve received a lot of feedback. And that feedback has resulted in some fairly significant, and unfortunately backwards incompatible, syntax changes – all for the better.

The big thing to take away from these changes is that valid JSON is now valid JCR. To some extent this was true with -06, but things like this were not:

[ "a", [ 1, 2, 3 ], "b" ]

Well, now it is (or at least will be in -07). But in doing this, we’ve had to move the repetition syntax to the end of the definitions. Whereas we use to do this:

[ :"a", [ 3 :integer ], :"b" ]

repetitions are now preceded with some syntactic sugar, the @, and moved to the end:

[ "a", [ integer @3 ], "b" ]

For a refresher on the concept of syntactic sugar:

In computer science, syntactic sugar is syntax within a programming language t hat is designed to make things easier to read or to express. It makes the language “sweeter” for human use: things can be expressed more clearly, more concisely, or in an alternative style that some may prefer.

Or in other words, the computer doesn’t need it. A JCR parser doesn’t need the @, but we’ve added it there so repetitions don’t get lost and appear to have a meaning more obvious than, “look, they forgot a comma”.

Syntactic sugar is one of those eye-of-the-beholder things, as I’ve learned through this process. And so… we’ve added more.

As you may recall, in JCR rules can be broken out and referenced by name. An example:

[ "a", ints, "b" ]

ints [ integer @3 ]

To the casual reader, that might seem confusing. Is ints a JCR thing? To make it clearer, we’ve decided that rule names must be immediately preceded by the $ character and the = character is to be used when naming rules. Thus:

[ "a", $ints, "b" ]

$ints = [ integer @3 ]

Now those aren’t all the changes we are working on, but those are the big ones. More to come…