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0 pointsvalenterry5y ago0 comments

There are no "special" methods in Scala. If you see something like "arr.map(_.nonEmpty).filter(a => a % 2)" in the standard library, you can use that syntax yourself too.

E.g. "arr.customlyFiltered()" is easy to do. Or even easier "arr.filter(myCustomFilter)". If something doesn't work out for you, please feel free to use e.g. scalafiddle.io and make it example, then you will be helped! :)

Scala is indeed not a high performant language. It is as fast as Java and compiles as fast as Java if you only use Java's features. However, then why use Scala in the beginning?

Scala is great for writing very maintainable and reusable code, especially with a big team and a lot of business logic. It is also great to "glue" things together like you can do it with Python. For these things it has more than sufficient performance in my opinion.

0 comments

tastyminerals25y ago

There is no straighforward elegant way of doing "obj.scalaMethod.myCustomMethod.scalaMethod.myCustomMethod" in Scala. I want to create a method and just inject it into the chain, no fiddling or ducktaping or using some black Scala magic.

"def myFun(a: String, b: Double): Boolean = {...}" and then "obj.mapValues.myFun.forall(_)" or just anything similar.

And yes, Scala is exactly the language when you need safe and maintainable code with far less unit tests required than in Java. But you have to invest into it and sometimes it is simply not worth it. The Scala2 to Scala3 migration situation makes things even worse unfortunately.

vvillena5y ago

There is a feature in Scala 2 that covers the specific thing you want: implicit classes. You can use them to add custom methods. It's clean and straightforward.

And it will be even easier in Scala 3, where this pattern is coded into an even simpler feature: extensions.

esarbe5y ago

In the Scala 2.x this can be done with an implicit class.

It's a bit cumbersome and not very use-case oriented (mechanism over intention) and so Scala 3 has introduced extension methods[0].

This gives you exactly what you want.

Since Scala 3 is pretty much completely backwards compatible (and with the use of Tasty you can use Scala 3 code in Scala 2.x projects), so I don't see the migration as a big problem. The Scala team has spent a lot of work to make the transition as painless as possible.

[0] https://dotty.epfl.ch/docs/reference/contextual/extension-me...

ph20825y ago

Thank you for URL. Just when I needed. Any idea when "Scala 3" can be production ready ?

1 more reply

shim__5y ago

It's not really black magic https://docs.scala-lang.org/overviews/core/implicit-classes.... but I don't really see why having a filter as a method should even be encouraged.

tastyminerals25y ago

Implicits are not encouraged in our code base and for a good reason.

This was just an example. It's not about filter at all but the general method chaining.

Here is example from D if I must:

    real[] fun(int[] arr) {
        return arr.map!(a => a.to!double / PI).array;   
    }

    void main()
    {
        int[] arr = 100.iota.array; // [0, 1, 2, 3, ...]
        real[] newArr = arr.map!(a=> a*2).array.fun); // [0, 0.63662, 1.27324, ...]
    }

I don't know how you can chain a custom method "fun" to the output of the "map" in Scala without duck typing. Why is this not possible when all conditions type-wise are met? Why you can chain std methods like map, filter, reduce, fold etc. but not custom ones?

2 more replies

valenterryOP5y ago

Assuming that your object is a list of tuples, then you can do:

    val myFun = (a: String, b: Int) => b % 2 == 0
    List("a" -> 1, "b" -> 2, "c" -> 3).map(myFun.tupled).forall(identity) // false
    List("a" -> 2, "b" -> 4, "c" -> 6).map(myFun.tupled).forall(identity) // true

But I think that's not what you mean... are you maybe looking for the "thrush" / |> operator? Or do you have some example from another language that does a better job and show how it looks there?

j / k navigate · click thread line to collapse

0 pointsvalenterry5y ago0 comments

There are no "special" methods in Scala. If you see something like "arr.map(_.nonEmpty).filter(a => a % 2)" in the standard library, you can use that syntax yourself too.

Scala is indeed not a high performant language. It is as fast as Java and compiles as fast as Java if you only use Java's features. However, then why use Scala in the beginning?

0 comments

tastyminerals25y ago

"def myFun(a: String, b: Double): Boolean = {...}" and then "obj.mapValues.myFun.forall(_)" or just anything similar.

vvillena5y ago

There is a feature in Scala 2 that covers the specific thing you want: implicit classes. You can use them to add custom methods. It's clean and straightforward.

And it will be even easier in Scala 3, where this pattern is coded into an even simpler feature: extensions.

esarbe5y ago

In the Scala 2.x this can be done with an implicit class.

It's a bit cumbersome and not very use-case oriented (mechanism over intention) and so Scala 3 has introduced extension methods[0].

This gives you exactly what you want.

[0] https://dotty.epfl.ch/docs/reference/contextual/extension-me...

ph20825y ago

Thank you for URL. Just when I needed. Any idea when "Scala 3" can be production ready ?

1 more reply

shim__5y ago

It's not really black magic https://docs.scala-lang.org/overviews/core/implicit-classes.... but I don't really see why having a filter as a method should even be encouraged.

tastyminerals25y ago

Implicits are not encouraged in our code base and for a good reason.

This was just an example. It's not about filter at all but the general method chaining.

Here is example from D if I must:

    real[] fun(int[] arr) {
        return arr.map!(a => a.to!double / PI).array;   
    }

    void main()
    {
        int[] arr = 100.iota.array; // [0, 1, 2, 3, ...]
        real[] newArr = arr.map!(a=> a*2).array.fun); // [0, 0.63662, 1.27324, ...]
    }

2 more replies

valenterryOP5y ago

Assuming that your object is a list of tuples, then you can do:

    val myFun = (a: String, b: Int) => b % 2 == 0
    List("a" -> 1, "b" -> 2, "c" -> 3).map(myFun.tupled).forall(identity) // false
    List("a" -> 2, "b" -> 4, "c" -> 6).map(myFun.tupled).forall(identity) // true

But I think that's not what you mean... are you maybe looking for the "thrush" / |> operator? Or do you have some example from another language that does a better job and show how it looks there?

j / k navigate · click thread line to collapse