so i have a vector of structs and i want to check if a name exists and return that index: (struct Person name age) (define v (vector (Person "bob" 44) ("alice" 33) ("steven" 22)) (??? (lambda (x) (string=? (person-name x) "alice") v)) ; should return the index location of alice, which is 1 basically is there a built in vector-memqthat takes a function instead of the value to search?

a memf for vector

I don’t think vector-memf exists.

actually memf doesn’t seem to return the index but the item itself :s

https://docs.racket-lang.org/collections/collections-api.html?q=index-of#%28def._%28%28lib._data%2Fcollection..rkt%29._index-of%29%29

thanks! a little off putting that i have to vector->list

you don’t

that function will work on vectors

:open_mouth:

(index-of (vector 1 2 3) 2 =), i get index-of: contract violation expected: list? given: ’#(1 2 3) argument position: 1st other arguments…:

that’s a different index-of

Sam pointed you toward the one in the collections package. The one you’re using is in racket/list.

(for/first ([p (in-vector people)] [i (in-naturals)] #:when (equal? (Person-name p) "bob")) i)

ahhhh

Just as I was typing this: (define (vector-index-of v p?) (for/first ([x (in-vector v)] [i (in-naturals)] #:when (p? x)) i)) (vector-index-of #(1 3 5 8 9) even?)

thanks guys!

One thing: if you do decide to go with collections, it tends to be a kind of all-in decision. It gives you a nice api for working with sequences of any kind, but it also produces lazy sequences, so if you try to mix-and-match functions from collections and ones from the built-in library, you can run into problems. So that could be a reason to go with the approach that @samdphillips and @soegaard2 are proposing.

im surprised vector-index-of isn’t built in :s

I’d guess that people would be receptive to a PR against racket/vector. (It should probably be called vector-memf for consistency with the list libs.)

It’s in srfi/43:

(require srfi/43) (vector-index even? #(1 3 5 8 9))

someone PR it pls :heart:

Would anyone like to help me test RacketCon streaming?

Thanks Michael, seemed fine?

Until the zoom feed froze/stopped, yes. Audio and video was fine for me.

so im writing s-expressions to a file and i don’t want the prefix of struct: with the name of the struct. I just want (atlas (frame)) #(#(struct:atlas (frame (w . 13) (x . 1146) (y . 34) (h . 8)) (source (w . 13) (x . 14) (y . 9) (h . 8)) (id . 532737) (duration . -1))) I’m reading the docs on how to customize display but how to customize the reader but im unsure how to use them

and the hash that comes before it, #(struct:atlas) . I think print is closer to what i want but i dont need the single quotes or (vector )

Depending on your use-case you may just want to use #:prefab structs. They read and write without hassle.

Is there a reason why struct doesn’t allow each automatic field to have a different automatic value?

you mean default value?

@kellysmith12.21 default values are a basically useless feature that is only still around for compatibility

why are default values a useless feature :0?

ah, before i write it to a file i can just replace all the ' and keywords. My usecase is that im serializing the s-xpressions in rust using https://docs.rs/serde-lexpr/0.1.1/serde_lexpr/

a bit hacky but lol (define final (string-append "#" (string-replace (string-replace (get-output-string acc) "vector" "") "'" ""))) lengthy but it works

Because they are limited and you should use a ‘smart’ constructor instead, where you can can specify default values but also handle domains and such and report more meaningful errors