Arne Babenhauserheide <arne_...@web.de> writes: >> For example, I've pondered the idea of making the "reader directive" >> mechanism (e.g. things like #!curly-infix) easily extensible. For >> example, we could perhaps arrange for 'read', when encountering "#!FOO" >> in the input stream, to look for a module named something like (system >> reader-directives FOO) which would extend the reader as needed. >> >> What do you think? > > That sounds useful on its own
After pondering this a bit, I’m worried that this might push people towards using reader directives as a replacement for syntax-definitions. One problem with that is that reader directives aren’t necessarily composable: While srfi-105 and srfi-119 compose well, the indentation parsing in srfi-119 and srfi-110 is mutually exclusive. For Racket I have the impression that this has the effect that the easiest way to experiment is to define a new language. The main reason why I think that is #lang typed/racket: Instead of creating a (define-typed ...) syntax, which would have been available in all languages, they added the (: ...) special form. (https://docs.racket-lang.org/ts-guide/quick.html) When you define something in a module, it can be used in other languages — including ecmascript and elisp. More exactly: You know that it can be (at least I think that — I used Guile features from ecmascript: Is there a limit to that which I did not hit?). With reader adjustments that’s different. However in Racket which started as a teaching language, this easier experimentation likely outweights the cost of fragmentation into different structures which cannot easily be used together. If you have lots of students going into lots of different directions, and you don’t actually want to recombine their work in specific applications, then you can easily afford the price of limited composability. But I’m biased in this: To avoid such fragmentation while providing indentation-based syntax (which cannot be done at all without adjusting the reader), I tried to keep the reader adaption in Wisp as minimal as possible — to defer to regular Scheme as quickly as possible. This should minimize friction from different approaches for tackling problems, making it easy for people who start with Wisp to understand any Scheme code (and vice versa). Best wishes, Arne -- Unpolitisch sein heißt politisch sein ohne es zu merken
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