tailrec | Groovy AST transformation to convert tail recursive methods | Code Analyzer library

I am receiving some large String content that contains several numbers demarcating sections.
I'm trying to modify the content in such a way that if a number is present, a line break is inserted.

So that something like: "1.This is one line. 2. This is another. 3. Here is one more."

gets modified to something like this:
"1.This is one line.
2. This is another.
3. Here is one more."

I tried solving it this way:

This simple regex implementation (scastie here) does not compile, where I expected it to. The error is at line 14, where an intermediate recursive call is interpreted as to break the @tailrec requirement. While this intermediate recursive call is indeed not in tail-call position, the actual last call of the expression is, making the complete expression tail-call optimized.

This line of reasoning can be illustrated by aliasing the intermediate recursive call, turning it into an 'arbitrary' call. When the this call is aliased by aliasMatches, the code compiles and executes as expected.

Why doesn't the compiler accepts the non-aliased implementation? Is this a practical limitation, or is there something wrong with the reasoning above? Is there a way to coax the compiler in accepting the first version (other than a complete accumulator-rewrite) that I'm missing?

(using Scala 2.13.5)

I have a recursive call as defined below:

I am writing a program in Scala using the IntelliJ IDEA IDE. And when I declare the return type of a method as Int, it shows an error and shows : Unit after the second bracket:

Can anyone please help me to understand the time and space complexity of algo to balance parenthesis

The task is to remove all occurrences of element in a list using Tail Recursion and Match expression.

In my code, I very often need to process a list by performing operations on an internal model. For each processed element, the model is returned and then a 'new' model is used for the next element of the list.

Usually, I implement this by using a tail recursive method:

I wrote the following function - which a little bit of JAVA way for me, I wanted to convert it to a more Scala way

Suppose I've got case class A(x: Int, s: String) and need to update a List[A] using a Map[Int, String] like that: