OLolooney·Nov 7, 2018
It appears that the most important restriction is on recursion:
> This is what guarantees the language is visibly pushdown: all recursion is explicitly delineated by special symbols.
> Plain recursion isn't allowed. Only two restricted kinds of recursion are available: guarded recursion and expression recursion.
So the Owl grammar itself qualifies:
https://github.com/ianh/owl/blob/master/grammar.owl
JSON certainly qualifies:
https://github.com/ianh/owl/blob/master/test/json.owl
I think the full JavaScript language would have qualified in the past, when anonymous functions could only be the explicitly delimited "function() {}"... but now with ES6 we have fat arrow functions (for example "(x,y) => x+y") so I think modern JavaScript can no longer be parsed with Owl. That's because you can write something like "f = x => y => z => x+y+z" which
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has no guard nor can it be parsed with expression recursion.
I do not think you can do a C-like language because of function types. But you can do a simpler, C-like language, for which they have an good example in the test directory:
https://github.com/ianh/owl/blob/master/test/something.owl