Open Source Rule Engines in Java

Manageability - Open Source Rule Engines Written In Java

I don't recall if someone has put together a list of open source Rule Engines that are written in Java. Here's the list I've accumulated so far...
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Converting Array to List in Scala

Now, this has to have a built-in somewhere in Scala, because it just seems too common. So, how to convert an Array to a List in Scala?

Why do I need this? I needed to drop to Java for some functionality, which in this case returns an Array. I wanted to get that Array into a List to practice my functional programming skillz.

**Update**: I figured out how to convert Arrays to Lists the Scala way. Turns out it's a piece of cake.

val myList = List.fromArray(Array("one", "two", "three"))

or

val myList = Array("one","two","three").elements.toList

The call to elements returns an Iterator, and from there you can convert to a List via toList. Nice.

Because my first version wasn't actually tail recursive, what follows is a true tail recursive solution, if I were to implement this by hand. The above, built in mechanism is much better, though.


object ArrayUtil {
def toList[a](array: Array[a]): List[a] = {
def convert(ar…
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I ported a JavaScript app to Dart. Here's what I learned.

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In which I port a snazzy little JavaScript audio web app to Dart, discover a bug, and high-five type annotations. Here's what I learned.

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Null-aware operators in Dart

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?? Use ?? when you want to evaluate and return an expression IFF another expression resolves to null.

exp ?? otherExp
is similar to

((x) => x == null ? otherExp : x)(exp)
??= Use ??= when you want to assign a value to an object IFF that object is null. Otherwise, return the object.

obj ??= value
is similar to

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?. Use ?. when you want to call a method/getter on an object IFF that object is not null (otherwise, return null).

obj?.method()
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((x) => x == null ? null : x.method())(obj)
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