does this syntactic sugar live in Arrow-kt by a na...

# arrow

[jimn]

does this syntactic sugar live in Arrow-kt by a named concept i can study up? it looks as close as i can make to the cat theory chalkboards lectures of f follows g

operator fun <A, B, C> Function1<A, B>.times(r: Function1<B, C>): (A) -> C = { x: A -> x.let(this).let(r) }

demonstrated below with the _***_'s

val bb2ba: (ByteBuffer) -> ByteArray = { bb: ByteBuffer -> ByteArray(bb.remaining()).also { bb[it] } }
val btoa: (ByteArray) -> String = { ba: ByteArray -> String(ba, Charsets.UTF_8) }
val trim: (String)->String  = String::trim
enum class TypeMemento(val bytes: Int?, val read: readfn, val write: writefn) { 
    txtInt(4, (bb2ba * btoa * trim * String::toInt), { a: ByteBuffer, b: Int? -> a.putInt(b ?: 0) } as writefn),

[jimn]

is this just a morphism??

[Jannis]

Isn't that just Functor.map on the Function1 functor? Either that or andThen might also work

[jimn]

https://next.arrow-kt.io/docs/apidocs/arrow-core-data/arrow.core/-function1/map.html this one ? is same as fmap in haskell? i am leaning toward.. finding the cheapest compiler hack to enable

operator fun `•`

to propose in a KEEP.

[Jannis]

yes those functions are almost the same. If you assume Function1<A, B> == (A) -> B .
Operator overloading is something kotlin deliberatly chose not to enable

[raulraja]

Also take a look at https://next.arrow-kt.io/docs/apidocs/arrow-syntax/arrow.syntax.function/index.html

[Jannis]

Sneaky raul showing off the new docs 😉

[jimn]

val bb2ba: (ByteBuffer) -> ByteArray = { bb: ByteBuffer -> ByteArray(bb.remaining()).also { bb[it] } }
val btoa: (ByteArray) -> String = { ba: ByteArray -> String(ba, Charsets.UTF_8) }
val trim: (String) -> String = String::trim
infix fun <O, R, F : (O) -> R> O.`•`(f: F) = this.let(f)
infix fun <A, B, R, O : (A) -> B, G : (B) -> R> O.`•`(b: G) = this * b
operator fun <A, B, R, O : (A) -> B> O.times(b: (B) -> R) =     { a: A -> a `•` this `•` (b) }
enum class TypeMemento(val bytes: Int?, val read: readfn, val write: writefn) {
    txtInt(4, (bb2ba `•` btoa `•` trim * String::toInt), { a: ByteBuffer, b: Int? -> a.putInt(b ?: 0) } as writefn),

this is as far as i can push it with infix alone

[jimn]

im fine with my own compiler front-end if it lets me elide backticks and drop in graph notation verbatim.

[jimn]

the USA is the only country without unicode keyboard keys

[jimn]

@raulraja thank you for the link