Fantastic, thank you ~slg
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Sunday, January 3, 2021 12:14 PM, Ryan Culpepper <[email protected]> wrote: > It's the consequence of two design goals: > > 1. The `module` form is separate from the `#%module-begin` syntax hook so > that the module's initial language can pick the hook macro that controls the > entire module body. > > 2. Racket's primitive syntax is designed so that it can be re-expanded. (The > `expand` operation should be idempotent.) Some of Racket's tools (for > example, debugging support) work by expanding code, instrumenting it, and > then re-expanding, compiling, and running the result. But a `#%module-begin` > hook macro can transform the module body in non-idempotent ways, so that hook > macro should only be called once. So the answer to "have I already run the > module's `#%module-begin` hook?" must be reflected in the fully-expanded > syntax of the module. > > Ryan > > On Sun, Jan 3, 2021 at 8:40 AM Michael MacLeod <[email protected]> > wrote: > >> Oops, sorry about interpreting your question wrong. Unfortunately I don't >> know the answer to your actual question. >> >> On Sat, Jan 2, 2021, 10:24 PM Sage Gerard <[email protected]> wrote: >> >>> I know about that. I asked why it was designed that way. >>> >>> Sent from ProtonMail mobile >>> >>> -------- Original Message -------- >>> On Jan 3, 2021, 12:18 AM, Michael MacLeod < [email protected]> >>> wrote: >>> >>>> There's an edge case of 'module' when only one form is provided which >>>> results in that form being partially expanded to determine if such >>>> expansion would lead to a #%plain-module-begin form. Otherwise (more than >>>> one form provided) they are wrapped in #%module-begin with no partial >>>> expansion occurring. >>>> >>>> I think this might be causing the discrepancy you witnessed. >>>> >>>> From the docs (https://docs.racket-lang.org/reference/module.html): >>>> >>>> If a single form is provided, then it is partially expanded in a >>>> module-begin context. If the expansion leads to #%plain-module-begin, then >>>> the body of the #%plain-module-begin is the body of the module. If partial >>>> expansion leads to any other primitive form, then the form is wrapped with >>>> #%module-begin using the lexical context of the module body; this >>>> identifier must be bound by the initial module-path import, and its >>>> expansion must produce a #%plain-module-begin to supply the module body. >>>> Finally, if multiple forms are provided, they are wrapped with >>>> #%module-begin, as in the case where a single form does not expand to >>>> #%plain-module-begin. >>>> >>>> (This response was adapted from one of my earlier replies to the mailing >>>> list. Search racket-users for "perplexed by macro-expansion behavior near >>>> #%module-begin" for more context). >>>> >>>> Best, >>>> Michael >>>> >>>> On Sat, Jan 2, 2021 at 8:26 PM Sage Gerard <[email protected]> wrote: >>>> >>>>> Why does Racket handle modules with exactly one form differently? >>>>> >>>>> I ran into a bug where modules in my module language won't expand if the >>>>> modules have exactly one form, so I'm just curious. >>>>> >>>>> (Wild guess: It's Racket's way of checking for a shortcut to end >>>>> expansion earlier) >>>>> >>>>> ~slg >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google Groups >>>>> "Racket Users" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send an >>>>> email to [email protected]. >>>>> To view this discussion on the web visit >>>>> [https://groups.google.com/d/msgid/racket-users/OVvZ0OK4_PfyvXCWfuvzDWBM5-ellmDvNmWchVmsCwAJb_rbSZkCkyraakcGsEMSCl2BsLsWtMXFhQcXY75IKhYiYYGQQEI7lVXLgGBbTCc%3D%40sagegerard.com](https://groups.google.com/d/msgid/racket-users/OVvZ0OK4_PfyvXCWfuvzDWBM5-ellmDvNmWchVmsCwAJb_rbSZkCkyraakcGsEMSCl2BsLsWtMXFhQcXY75IKhYiYYGQQEI7lVXLgGBbTCc%3D%40sagegerard.com?utm_medium=email&utm_source=footer). >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Racket Users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> [https://groups.google.com/d/msgid/racket-users/CACehHmBvs5KK4vQmwio93D1NZ9hTOoSv-Qkm8XOjF%2B4JWDOiHg%40mail.gmail.com](https://groups.google.com/d/msgid/racket-users/CACehHmBvs5KK4vQmwio93D1NZ9hTOoSv-Qkm8XOjF%2B4JWDOiHg%40mail.gmail.com?utm_medium=email&utm_source=footer). -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/Chmb4Sh3Pm8Y0D-qf19jw8Z0aM6AYGMrDfOZn2FzzrgrDNINR_K7QV5beIaJPiVakohvBLgSeSHoesndVxQOTaj068otESk8ROXGif0RHWY%3D%40sagegerard.com.
