Am Di., 22. Sept. 2020 um 18:05 Uhr schrieb Lassi Kortela <xxxxxx@lassi.io>: > > >> (define-library (scheme list) > >> (extends (srfi 1)) > > > > I think there is a fundamental difference between `(alias-for (srfi > > 1))` and `(extends (srfi 1))`. In the former case, we just have one > > library with two names. In particular, the library only has to be > > loaded (and expanded) once. In the latter case, we have to libraries > > (which just may happen to be equivalent) that have to be loaded and > > expanded separately. So it even makes sense to have both forms > > separately. The `extends` form would expand into an import declaration > > together with a corresponding export declaration. It makes sense to > > allow that the `extends` form is decorated with `only`, `prefix`, > > `rename`, and `except`. > > There doesn't have to be a fundamental difference if > > (define-library (foo) (alias-for (bar))) > > is parsed magically as something different from an ordinary > `define-library`. I meant that there is a fundamental difference between a mere library alias and a library defined through a hypothetical "extend" library declaration: (define-library (srfi 158) (extend (srfi 121)) (export make-accumulator ...) (import (scheme base) ...) (begin ...)) The top-level library environment of an aliased library will be shared, while the top-level library environment of a library extending another one will be a new one. This can be observed through hygiene-bending given a sufficiently powerful macro system. > But I agree that `define-library-alias` is more elegant. > > The symmetry with Chez Scheme `alias` (which you refer to in your > pre-SRFI <https://github.com/mnieper/srfi-212>) is nice. Already implemented in Unsyntax. :) Basically just two lines of non-trivial code.
