Re: [racket-users] Cannot use case+else inside match+else
And because it is nothing else but a usual binding, it's possible to prefix-in or rename-in as in (require (prefix-in r: racket/base)) (case 5 [r:else 'ok]) On Wed, Feb 27, 2019 at 7:32 AM Laurent wrote: > > Good point. I wasn't sure that would work---it does. > > On Wed, Feb 27, 2019 at 1:28 PM Jens Axel Søgaard > wrote: >> >> I suppose you could (re)require it again. >> >> ons. 27. feb. 2019 kl. 14.19 skrev Laurent : >>> >>> Wait, that means that in an interactive session, if you ever happen to >>> redefine `else', you can't use `case' anymore? >>> >>> On Tue, Feb 26, 2019 at 5:03 AM Ben Greenman >>> wrote: Here's a suggestion for the docs: https://github.com/racket/racket/pull/2505 -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. >>> >>> -- >>> 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 racket-users+unsubscr...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >> >> -- >> -- >> Jens Axel Søgaard >> -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
Good point. I wasn't sure that would work---it does. On Wed, Feb 27, 2019 at 1:28 PM Jens Axel Søgaard wrote: > I suppose you could (re)require it again. > > ons. 27. feb. 2019 kl. 14.19 skrev Laurent : > >> Wait, that means that in an interactive session, if you ever happen to >> redefine `else', you can't use `case' anymore? >> >> On Tue, Feb 26, 2019 at 5:03 AM Ben Greenman >> wrote: >> >>> Here's a suggestion for the docs: >>> >>> https://github.com/racket/racket/pull/2505 >>> >>> -- >>> 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 racket-users+unsubscr...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- >> 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 racket-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. >> > -- > -- > Jens Axel Søgaard > > -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
I suppose you could (re)require it again. ons. 27. feb. 2019 kl. 14.19 skrev Laurent : > Wait, that means that in an interactive session, if you ever happen to > redefine `else', you can't use `case' anymore? > > On Tue, Feb 26, 2019 at 5:03 AM Ben Greenman > wrote: > >> Here's a suggestion for the docs: >> >> https://github.com/racket/racket/pull/2505 >> >> -- >> 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 racket-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. >> > -- > 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 racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- -- Jens Axel Søgaard -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
Wait, that means that in an interactive session, if you ever happen to redefine `else', you can't use `case' anymore? On Tue, Feb 26, 2019 at 5:03 AM Ben Greenman wrote: > Here's a suggestion for the docs: > > https://github.com/racket/racket/pull/2505 > > -- > 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 racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
Here's a suggestion for the docs: https://github.com/racket/racket/pull/2505 -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
Previously on this program... https://lists.racket-lang.org/dev/archive/2013-May/thread.html [racket-dev] else clauses: possible change to match? On Mon, Feb 25, 2019 at 10:59 PM Greg Hendershott wrote: > Yep, I also spent a non-zero number of years not even realizing "else" > wasn't a magic literal for match. And then remembering to use _ > instead, as Sorawee suggested. > > > I think this shows why it's usually better for syntax to use > #:keywords instead of literals? If cond and case used #:else, this > wouldn't be a problem. > > (Racket inherited those from Scheme. But we don't have to follow that > example in our own, new macros.) > > -- > 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 racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
Yep, I also spent a non-zero number of years not even realizing "else" wasn't a magic literal for match. And then remembering to use _ instead, as Sorawee suggested. I think this shows why it's usually better for syntax to use #:keywords instead of literals? If cond and case used #:else, this wouldn't be a problem. (Racket inherited those from Scheme. But we don't have to follow that example in our own, new macros.) -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
I have been bitten by this one too, it is a bit pernicious. Perhaps we can adjust the documentation to make more clear that `else` isn't special in `match`? Robby On Mon, Feb 25, 2019 at 6:51 PM Sorawee Porncharoenwase wrote: > > I usually use _ for the otherwise case because I usually match on an > identifier, so I have an id to refer to the matched value already if I need > to. The only case I don’t use _ is when I compute something inside the match > and also need to use its result: > > (match (foo bar) > [... ...] > [result-of-foo-bar ...]) > > > On Mon, Feb 25, 2019 at 4:41 PM Shu-Hung You > wrote: >> >> Ah! >> >> Thank you for pointing this out. I've always thought that `else' is >> treated as a keyword in `match' just as what `cond' does. That >> explains everything. >> >> On Mon, Feb 25, 2019 at 6:35 PM Sam Tobin-Hochstadt >> wrote: >> > >> > This is because 'case' expects a particular binding for 'else', but you >> > shadowed it with 'match', which does not treat 'else' differently than any >> > other identifier. >> > >> > Sam >> > >> > On Mon, Feb 25, 2019, 7:33 PM Shu-Hung You >> > wrote: >> >> >> >> When using a case expression with an else clause in inside a match >> >> expression, the expander complains about case having a bad syntax. >> >> However, the use of case expressions outside of match are fine. Is >> >> there anyway to get around this? >> >> >> >> Currently, I just replace it with another match. >> >> >> >> #lang racket/base >> >> >> >> (require racket/match) >> >> >> >> (match 6 >> >> [else >> >>(case 5 >> >> [else 7])]) >> >> >> >> #| >> >> unsaved editor:8:6: case: bad syntax (not a datum sequence) at: else >> >> in: (case 5 (else 7)) >> >> #(78 4) >> >> |# >> >> >> >> -- >> >> 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 racket-users+unsubscr...@googlegroups.com. >> >> For more options, visit https://groups.google.com/d/optout. >> >> -- >> 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 racket-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. > > -- > 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 racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
I usually use _ for the otherwise case because I usually match on an identifier, so I have an id to refer to the matched value already if I need to. The only case I don’t use _ is when I compute something inside the match and also need to use its result: (match (foo bar) [... ...] [result-of-foo-bar ...]) On Mon, Feb 25, 2019 at 4:41 PM Shu-Hung You < shu-hung@eecs.northwestern.edu> wrote: > Ah! > > Thank you for pointing this out. I've always thought that `else' is > treated as a keyword in `match' just as what `cond' does. That > explains everything. > > On Mon, Feb 25, 2019 at 6:35 PM Sam Tobin-Hochstadt > wrote: > > > > This is because 'case' expects a particular binding for 'else', but you > shadowed it with 'match', which does not treat 'else' differently than any > other identifier. > > > > Sam > > > > On Mon, Feb 25, 2019, 7:33 PM Shu-Hung You < > shu-hung@eecs.northwestern.edu> wrote: > >> > >> When using a case expression with an else clause in inside a match > >> expression, the expander complains about case having a bad syntax. > >> However, the use of case expressions outside of match are fine. Is > >> there anyway to get around this? > >> > >> Currently, I just replace it with another match. > >> > >> #lang racket/base > >> > >> (require racket/match) > >> > >> (match 6 > >> [else > >>(case 5 > >> [else 7])]) > >> > >> #| > >> unsaved editor:8:6: case: bad syntax (not a datum sequence) at: else > >> in: (case 5 (else 7)) > >> #(78 4) > >> |# > >> > >> -- > >> 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 racket-users+unsubscr...@googlegroups.com. > >> For more options, visit https://groups.google.com/d/optout. > > -- > 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 racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
Ah! Thank you for pointing this out. I've always thought that `else' is treated as a keyword in `match' just as what `cond' does. That explains everything. On Mon, Feb 25, 2019 at 6:35 PM Sam Tobin-Hochstadt wrote: > > This is because 'case' expects a particular binding for 'else', but you > shadowed it with 'match', which does not treat 'else' differently than any > other identifier. > > Sam > > On Mon, Feb 25, 2019, 7:33 PM Shu-Hung You > wrote: >> >> When using a case expression with an else clause in inside a match >> expression, the expander complains about case having a bad syntax. >> However, the use of case expressions outside of match are fine. Is >> there anyway to get around this? >> >> Currently, I just replace it with another match. >> >> #lang racket/base >> >> (require racket/match) >> >> (match 6 >> [else >>(case 5 >> [else 7])]) >> >> #| >> unsaved editor:8:6: case: bad syntax (not a datum sequence) at: else >> in: (case 5 (else 7)) >> #(78 4) >> |# >> >> -- >> 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 racket-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
This is because 'case' expects a particular binding for 'else', but you shadowed it with 'match', which does not treat 'else' differently than any other identifier. Sam On Mon, Feb 25, 2019, 7:33 PM Shu-Hung You < shu-hung@eecs.northwestern.edu> wrote: > When using a case expression with an else clause in inside a match > expression, the expander complains about case having a bad syntax. > However, the use of case expressions outside of match are fine. Is > there anyway to get around this? > > Currently, I just replace it with another match. > > #lang racket/base > > (require racket/match) > > (match 6 > [else >(case 5 > [else 7])]) > > #| > unsaved editor:8:6: case: bad syntax (not a datum sequence) at: else > in: (case 5 (else 7)) > #(78 4) > |# > > -- > 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 racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Cannot use case+else inside match+else
I may be missing something obvious, here, but why are you using the name “else” to bind the result in the match clause? I usually use the name “other”, which might solve your problem. John > On Feb 25, 2019, at 4:32 PM, Shu-Hung You > wrote: > > When using a case expression with an else clause in inside a match > expression, the expander complains about case having a bad syntax. > However, the use of case expressions outside of match are fine. Is > there anyway to get around this? > > Currently, I just replace it with another match. > > #lang racket/base > > (require racket/match) > > (match 6 > [else > (case 5 > [else 7])]) > > #| > unsaved editor:8:6: case: bad syntax (not a datum sequence) at: else > in: (case 5 (else 7)) > #(78 4) > |# > > -- > 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 racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[racket-users] Cannot use case+else inside match+else
When using a case expression with an else clause in inside a match expression, the expander complains about case having a bad syntax. However, the use of case expressions outside of match are fine. Is there anyway to get around this? Currently, I just replace it with another match. #lang racket/base (require racket/match) (match 6 [else (case 5 [else 7])]) #| unsaved editor:8:6: case: bad syntax (not a datum sequence) at: else in: (case 5 (else 7)) #(78 4) |# -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
