What is the relationship between functional and imperative paradigms?

Question

C++ / C#

I downloaded a book about Functional Programming in pure C:

On page 1, the very first paragraph put me in an awkward position, how functional programming can be connected with the imperative paradigm:

Answer 1

No connection. I translate the highlighted sentence: "This book was written for those who are familiar with functional programming in SML and want to learn imperative programming in C."
Below in the text there is also: "functional and imperative languages ​​can be used to write programs in different styles: in SML you can write in an imperative style, and in C in a functional one. But programs written in this way look alien . " And the book, apparently, is about how to write in C in such an alien style that it is ala SML. Here's an idea.
PS I leafed through the book a bit, and it seems that there is just a tutorial on how to transfer from SML to C. With examples in one language and translating them into another, along with an explanation of what is happening.