If you are willing to go to extraordinary lengths, then yes any programming language can be written in a declarative style, at least some part of the program. Some parts of a Java or PHP program can be written declaratively.
In the Nix language context however, they mean declarative and functional like Prolog.
There is also Guix which uses Scheme to declare dependencies, and Scheme is not a declarative language. Scheme is a functional language, but it can be easily written in a declarative style.
In the Nix language context however, they mean declarative and functional like Prolog.
There is also Guix which uses Scheme to declare dependencies, and Scheme is not a declarative language. Scheme is a functional language, but it can be easily written in a declarative style.