You can also do anything in assembly. You just won't, practically speaking. "Can do" in that case is shorthand for "is not inordinately expensive and difficult

You can also do anything in assembly. You just won't, practically speaking. "Can do" in that case is shorthand for "is not inordinately expensive and difficult to do". What I meant was not "you can write programs with FP that you can't in an imperative language" (which is obviously not true); what I meant was "you can syntactically and semantically do things in functional languages that you can't express in imperative languages within a reasonable amount of effort". > what makes FP useful? As I said, this is a book-length topic that I can't hope to spell out. The reason I listed those concepts is that learning about them will help to impart understanding of why FP is useful.