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spinningslate 4y ago

>It is no fun writing external DSLs when you're stuck with your grandfather's parser generator. Agreed. I've tried various different approaches to building external DSLs, from fully hand-written to language workbenches like xtext [0] and spoofax [1]. I always end up back at hand written, often because of error handling. Creating meaningfully helpful error handling with parser generators always seems hard. >If we had grammars that were really extensible Grammar composition is hard. Canonical BNF is top down, meaning alternate clauses are complete and closed in most parser generators. One notable exception is SF3[2] (part of Spoofax). It doesn't require alternate clauses to be grouped and so can support composable languages. It's the most flexible parser-generator I've used, and the syntax is pretty nice too. Fun fact: SDF3 and Spoofax come from Eelco Visser's group at TU-Delft - the same group that originated Scope Graphs, the basis for Github's Stack Graphs [3]. [0] http://www.eclipse.org/Xtext/ http://www.eclipse.org/Xtext/ [1] https://www.spoofax.dev/ https://www.spoofax.dev/ [2] https://eelcovisser.org/publications/2020/AmorimV20.pdf https://eelcovisser.org/publications/2020/AmorimV20.pdf [3] https://news.ycombinator.com/item?id=29500602 https://news.ycombinator.com/item?id=29500602

thaumasiotes 4y ago
> Grammar composition is hard. Composing grammars may not be possible, but it's easy to define a new grammar that provides the composition of two other grammars along with boilerplate that serves the purpose of determining whether you're in a "grammar A" context or a "grammar B" context. You just need tokens that aren't valid in grammar A or grammar B. No statement in such a grammar would be valid in either subgrammar, because of the boilerplate, but they would all be trivially reducible to valid statements in the appropriate subgrammar.
- PaulHoule 4y ago
  It drives people nuts but I say there are many characters in Unicode https://unicode-table.com/en/sets/quotation-marks/ https://unicode-table.com/en/sets/quotation-marks/ if you need a new kind of quote, so you could write Integer index = 77; Statement s = « SELECT COUNT(*) FROM that WHERE x = @index »; People ask me "How do you type those on the keyboard?" and I say, "I don't type them on the keyboard, I cut and paste them." I use >128 codepoints all the time and mostly I don't need to because autocomplete works with them. No reason you can't write out.println(√(41.0))
  - lproven 4y ago
    I suggest learning to use the Compose key. For instance with no clipboard use at all, it enables «this». Compose+<+< and then to close compose+>+> Also see “curly” quotes: compose+<+" and compose+>+". This illustrates the power of composing: I had forgotten the shortcut, because I rarely use it, but I was able to guess it in 3 tries.