The more I read about these kind of article the more I am amazed that our digital future is at hand in utterly incompetent people.
This person clearly have no understanding of monadic error (AKA Maybe/option monad or slightly more advanced Either monad), which is the first monad we teach at a class targeting second year undergrad.
The performance comparison is just plain factual error. The functional error code will continue to compute n2 when computation of n1 failed; the same do not happen in the exception version. If you compare codes with completely different traces, of course they will have different performance…
A properly implemented monadic error will return as soon as compute for n1 failed, and never execute the rest of the code. This is the default and idiomatic behavior in Haskell, OCaml, F#, and rust. This performance problem doesn’t even happen in LINQ-style handling like in C# and Kotlin (maybe also Typescript?).
The point of monadic error is that its control flow is local, whereas exception is non-local. Specifically, the exception can be handled and occur anywhere in the code base, with no indication on the type level. So programmers will be constantly worrying about whether the exception in a function call is properly handled.
Even worse, when you try to catch a certain error, there is always the risk to accidentally catch similar exceptions in a library call or someone else’s code. Writing good code with try-catch requires a lot of principle and style guides. But unlike monads, these principle and rules cannot be enforced by the type system, adding extra burden to programmers.
In fact, we have known for a long time that non-local control flows (goto, break, contiune, exception, long jump) are the breeding ground for spaghetti code. As an evidence, many non-local control flows (goto, long jump) are baned in most languages.
That being said, there are certainly cases, with proper documentation, that exception style is easy to write and understand. But I think they are very specific scenarios, which have to be justified on a case-by-case basis.
In Maybe monadic, its monadic bind will automatically resolves any failed computation, and don’t need explicit checking.
for example, the code in Haskell looks something like the following:
fib: Int -> Int -> Maybe Int fib max_depth idx = do guard (0 <= max_depth) n1 <- fib (max_depth - 1) (idx - 1) n2 <- fib (max_depth - 1) (idx - 2) return (n1 + n2)Haskell type class system automatically figures out this is a maybe monad, and check for error accordingly.
Notice, unlike the C code the author provide, this haskell code will exit immediately when
n1failed and never computen2, similar to the behavior of the exception code. Thus I believe his point about performance is at least unjustified, if not wrong.Another interesting fact about this code is that there is nothing that is built into the compiler/interpretor (except the
doexpression, which is just a minor syntactical sugar). For this code, the compiler designers don’t need to design special semantics for raise and catch. Everything here,guard,return, and theMaybemonad (which is in charge of propagating errors) is defined by the user, using normal functions, no metaprogramming involved.Yes, unlike monad, the error in algebraic effect is propagated by the compiler/interpretor, instead of user defined. But unlike implicit effect, explicit effect (algebraic effect, throwable, etc.) makes it clear how the code can go wrong.
Although explicit error through monad or algebraic effect is more clear in general, there are special cases where explicit effect is undesirable. One such example is effect pollution: low-level effects that are unlikely to cause impure behaviors are unnecessarily propagated through the call stack. This problem can make the code more verbose and difficult to handle.