This page is part of the web mail archives of SRFI 83 from before July 7th, 2015. The new archives for SRFI 83 contain all messages, not just those from before July 7th, 2015.
I'm not sure what to think about this proposal. On the one hand, it provides a long-yearned facility with a standard syntax, simple, easy to understand and relatively generic. On the other hand, it is un-Scheme-like in many ways -- probably because many of the existing implementations, after which this SRFI has been modelled, are that too. Modules are not objects. They are identified by strings, not even symbols. The syntax doesn't seem to be very generic nor neutral about execution phases: it presupposes there to be two. The library system is accessible to neither phase; both phases must operate "within it". The syntax is not integrated with the core language, but is an add-on. What I find particularly problematic is that here _protocol_ is specified before _mechanism_. First-class reified continuations were specified before exception and indeterminism facilities, because continuations are the mechanism, and exceptions are a protocol for using that mechanism. Vectors were specified before records, because vectors are the mechanism and records are a protocol for using that mechanism. Admittedly, define-syntax (a protocol) was specified before specifying what syntax transformers are, but now we have Andre's simple, elegant and versatile macro mechanism that allows us to bring syntax and syntax transformers back into the realm of Scheme basic data types. Remember this sentence? "Programming languages should be designed not by piling feature on top of feature, but by removing the weaknesses and restrictions that make additional features appear necessary." Scheme people should think as much as possible how to provide a powerful enough core that extensions can be made in Scheme. Having devised sufficient facilities for libraries in the core, SRFI's can standardise on a library syntax. By removing restrictions, such as the artificial barrier between the library engine and the evaluation engine, we obtain a language that is both more expressive and simpler. It happens that R5RS already has a facility that _almost_ implements modules. This facility is called an "environment". Environments contain values for symbols, exactly like modules do. They only lack a few properties to be used as full-fledged modules: the ability to create new, empty environments and the possibility to query an environment for the bindings it contains. If we continue on the track now chosen, we will have a language full of half-fledged utilities, all somewhat similar, all restricted in different ways: environments, modules, hash tables, objects, and records. That's not a nice state to be in. How about specifying the mechanism in the report, and leave protocol to SRFI's? It's slow, but that's the Scheme way, at least it has been. It has the additional bonus that the language gets more powerful, more SRFI's can be written in pure Scheme (because of the reflective abilities), and programmers that really dislike the library syntax can fix it. IOW, freedom, and possibility to continue language research, in Scheme. Panu -- personal contact: panu.kalliokoski@xxxxxxxxxxx, +35841 5323835 technical contact: atehwa@xxxxxx, http://www.iki.fi/atehwa/ PGP fingerprint: 0EA5 9D33 6590 FFD4 921C 5A5F BE85 08F1 3169 70EC