That doesn't make the application not-procedural. If it's having side effects, it's procedural in a sense.
Order, here, is not about inbound event order, but about ordered steps in processing any one event.
“Procedural” is a structural paradigm; unstructured imperative code (old-school BASIC) has side effects but is not procedural in any sense (it is part of the broader category of imperative languages.) Also, “procedural” (or “imperative” or “functional”) is an attribute of programming languages, not applications/systems: Haskell is a pure functional programming languages, in which evaluating functions has no side effects, but it can define systems that have effects.
> Also, “procedural” (or “imperative” or “functional”) is an attribute of programming languages, not applications/systems:
It can be an attribute of programs regardless of language. It is possible to write functional-style code in C and procedural code in Haskell (just do everything in the IO monad!).
> Haskell is a pure functional programming languages, in which evaluating functions has no side effects, but it can define systems that have effects.
That's a bit of a fiction. Pure functions are pure, yes, but you can have impure functions -- Haskell is only interesting because you can have impure functions (otherwise every Haskell program would compile down into a constant), and what's really interesting about Haskell is the ideas that have evolved in its community about how to deal with impure functions.
Not in Haskell, you can't.
> Haskell is only interesting because you can have impure functions
No, it's interesting because it provides a way of representing series of effectful operations that are distinct from its functions, which are pure.
> otherwise every Haskell program would compile down into a constant
Every program in any language that is compiled compiles down to a constant (which is, itself, usually a program, often an imperative one in a native or virtual machine language); but in Haskell, each program is (in the model of the language, not merely what they compile to) normally a constant, non-function expression, most commonly of type IO ().
It's true that values of type IO a are isomorphic to “impure nullary functions returning a” in a language which has impure functions, but they aren't functions in Haskell, and can't be called from functions, they can only be operated on as values within the language.
> Every program in any language that is compiled compiles down to a constant ...
Sigh, yes, the compiled program is constant, but you know what I meant: a constant value, such as a number, that the program is expected to output. Let's not be this pedantic.
