Is this a case of implicit "but", or a comma-splice sentence?

Question

In a computer book (Programming in Haskell, second edition — Graham Hutton), I found the following sentence.

This new edition not only adds many more concrete examples of concepts introduced throughout the book, it also introduces the novel Haskell concepts of foldable and traversable.

Since the first clause contains not only, I read it as follows.

This new edition not only adds many more concrete examples of concepts introduced throughout the book, but it also introduces the novel Haskell concepts of foldable and traversable.

Is this a case of implicit "but", or is the sentence a comma-splice sentence?

If it's the first case, is not only sufficient to assume there is an implicit but in a clause?

Answer 1

According to Cambridge Dictionary, this is a very likely a "not only... but also..." situation.

Sometimes, certain parts of the sentence are implicitly understood, so speakers / writers omit them.

In the case of the sentence you presented, it does sound like something is missing.

Conclusion: your assumption of a missing "but" is correct.

A better way to write it could be:

This new edition adds many more concrete examples of concepts introduced throughout the book. It also introduces the novel Haskell concepts of foldable and traversable.

Splitting the entire thing in two parts makes it easier to understand, and avoids some potential confusions.