Re: [racket-users] Struct subtype with default/fixed value of super-type
To go further, if you wonder how to make this work for `match` and inheriting, see this stackoverflow question: https://stackoverflow.com/questions/55262818/how-to-override-a-struct-constructor-while-still-providing-the-struct-metadata-f On Mon, Mar 18, 2019 at 3:08 PM Marc Kaufmann wrote: > While I did know that I could define my own, I was going to do it while > providing-out another function make-fish and make-shark, but it's nice to > know that this allows me to locally define make-fish, while it looks to the > outside like (fish ...). > > Thanks to including sufficient numbers of mundane bugs in my code (all > well-maintained in version control, for quick deployment on docker), I > rarely get to worry about phases - it just isn't where the highest gains > are. :-) > > On Mon, Mar 18, 2019 at 2:46 PM Jérôme Martin > wrote: > >> Once you discover that the default constructor for a struct is just a >> simple procedure that was generated for you, it's not that big of deal to >> just make your own and export it like this: >> >> (provide >> (except-out (struct-out fish) fish) >> (rename-out (make-fish fish))) >> >> All the code relying on it will still work. >> Except I guess if you pass through different phase levels, it becomes a >> bit more complicated because you have a syntax attached at compile-time to >> the identifier. But that's another issue. >> Correct me if I'm wrong. >> >> On Monday, March 18, 2019 at 2:11:46 PM UTC+1, Marc Kaufmann wrote: >>> >>> Yes, I saw that, the problem is that I want to be able to set a >>> (potentially different) default value for the sub-type shark than for the >>> sub-type guppy. So if I set the value to 'big for all `fish`, then I can't >>> do that. Essentially, I'd need an #:auto for every sub-type, but the #:auto >>> refers to a parent/super field. >>> >>> I'll just run with defining a custom constructor. >>> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "Racket Users" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/racket-users/TthsE0FZDB0/unsubscribe. >> To unsubscribe from this group and all its topics, 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] Struct subtype with default/fixed value of super-type
While I did know that I could define my own, I was going to do it while providing-out another function make-fish and make-shark, but it's nice to know that this allows me to locally define make-fish, while it looks to the outside like (fish ...). Thanks to including sufficient numbers of mundane bugs in my code (all well-maintained in version control, for quick deployment on docker), I rarely get to worry about phases - it just isn't where the highest gains are. :-) On Mon, Mar 18, 2019 at 2:46 PM Jérôme Martin wrote: > Once you discover that the default constructor for a struct is just a > simple procedure that was generated for you, it's not that big of deal to > just make your own and export it like this: > > (provide > (except-out (struct-out fish) fish) > (rename-out (make-fish fish))) > > All the code relying on it will still work. > Except I guess if you pass through different phase levels, it becomes a > bit more complicated because you have a syntax attached at compile-time to > the identifier. But that's another issue. > Correct me if I'm wrong. > > On Monday, March 18, 2019 at 2:11:46 PM UTC+1, Marc Kaufmann wrote: >> >> Yes, I saw that, the problem is that I want to be able to set a >> (potentially different) default value for the sub-type shark than for the >> sub-type guppy. So if I set the value to 'big for all `fish`, then I can't >> do that. Essentially, I'd need an #:auto for every sub-type, but the #:auto >> refers to a parent/super field. >> >> I'll just run with defining a custom constructor. >> > -- > You received this message because you are subscribed to a topic in the > Google Groups "Racket Users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/racket-users/TthsE0FZDB0/unsubscribe. > To unsubscribe from this group and all its topics, 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] Struct subtype with default/fixed value of super-type
Once you discover that the default constructor for a struct is just a simple procedure that was generated for you, it's not that big of deal to just make your own and export it like this: (provide (except-out (struct-out fish) fish) (rename-out (make-fish fish))) All the code relying on it will still work. Except I guess if you pass through different phase levels, it becomes a bit more complicated because you have a syntax attached at compile-time to the identifier. But that's another issue. Correct me if I'm wrong. On Monday, March 18, 2019 at 2:11:46 PM UTC+1, Marc Kaufmann wrote: > > Yes, I saw that, the problem is that I want to be able to set a > (potentially different) default value for the sub-type shark than for the > sub-type guppy. So if I set the value to 'big for all `fish`, then I can't > do that. Essentially, I'd need an #:auto for every sub-type, but the #:auto > refers to a parent/super field. > > I'll just run with defining a custom constructor. > -- 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] Struct subtype with default/fixed value of super-type
Yes, I saw that, the problem is that I want to be able to set a (potentially different) default value for the sub-type shark than for the sub-type guppy. So if I set the value to 'big for all `fish`, then I can't do that. Essentially, I'd need an #:auto for every sub-type, but the #:auto refers to a parent/super field. I'll just run with defining a custom constructor. On Sat, Mar 16, 2019 at 8:24 AM Luis Sanjuán wrote: > Maybe #:auto/#:auto-value is what you want: > > ``` > (struct fish (name [size #:auto]) > #:auto-value 'big > #:transparent) > (struct shark fish (scares-people?) #:transparent) > > (define white-shark (shark "The big white" #t)) > ``` > > -- > You received this message because you are subscribed to a topic in the > Google Groups "Racket Users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/racket-users/TthsE0FZDB0/unsubscribe. > To unsubscribe from this group and all its topics, 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] Struct subtype with default/fixed value of super-type
Maybe #:auto/#:auto-value is what you want: ``` (struct fish (name [size #:auto]) #:auto-value 'big #:transparent) (struct shark fish (scares-people?) #:transparent) (define white-shark (shark "The big white" #t)) ``` -- 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] Struct subtype with default/fixed value of super-type
Hi all, suppose I have a struct `(struct fish (size name) #:transparent)` and a sub-type `(struct shark fish (scares-people?) #:transparent)`. What if I want all sharks to have size 'large by default whenever I create one, so that I create them via: (define white-shark (shark "The big white" #t)) rather than (define white-shark (shark 'big "The big white" #t)) Is that possible to do, other than defining my own wrapper? If it is not possible with the current structures, I guess it would be bad practice to overwrite the `shark` constructor, and rather create a `my-shark` constructor to avoid (hypothetical) reader of my code wouldn't get confused. Best, Marc -- 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.
