pyret-lang

You can actually use ";" as an alias for "end" in Pyret, so you could write: data BinTree: | leaf | node(value, left, right); We use "end" or ";" in order to have unambiguous delimiters for the ends of syntactic forms and avoid needing to depend on whitespace (we added some discussion on pyret.org about our philosophy on indentation and why we don't want to depend on whitespace). Making that leading pipe optional is a good idea. I made an issue for it, we'll think about if it'll break or confuse anything and add it if it doesn't: https://github.com/brownplt/pyret-lang/issues/106

Pyret looks like a there's a lot going on, based on the examples. It has implicit returns, special purpose syntax for data structures, iterators, assertions, refinements, etc. Having support for more stuff makes it less suitable as a teaching language, not more. Pyret looks like a has the good bits of Python plus a whole bunch of other cool stuff. But the language is pretty complex as a result. Cool? Yup! Good for teaching? Probably not. Take a look at the grammar and judge for yourself: https://github.com/brownplt/pyret-lang/blob/master/src/lang/...