I’m presently working on a problem which uses traversal of TypeScript file syntax trees.
I can reasonably assume that we will never get a file with a deep enough syntax tree which would cause a stack overflow.
A manually managed stack might seem safer, but as pointed out by this article the code would be more complicated and, in my case, for no good reason.
First: that common programming languages use the limited call stack for implementing recursion is an artifact of the programming language (implementation). One can, for example, use a stack data structure for implementing DFS instead of using the call stack; it would be no problem for a programming language implementation to use a similar method for implementing recursion.
This said: there actually exist two kinds of recursion (barely every computer science textbooks at most barely mentions this):
1. "normal" recursion (with all its problems such as potential stack overflow etc.)
2. tail recursion with guaranteed tail-call elimination (TCE) in the programming language semantics; then recursion basically behaves "like loops".
I want to clarify that it is a common exercise to convert a program that uses "normal" recursion to one that uses tail-recursion, just like it is a common exercise to convert such a program to one that uses imperative style.
But in this particular case I'm using JavaScript (since at this time it has the best libraries for working with TypeScript ASTs) running under Node.js, and my understanding is that is has no tail call optimization.
The other language I mostly work in is C#, which also similarly lacks it.
So, at this time in the languages I work in, I need to consider possible stack overflows whenever I use recursion.
Personally I tend to find the iterative approach easier to follow when no actual stack is needed, i.e. in the tail-call case.
What if eve constructs a file specifically so that you get stack overflow?
The author is trying to demonstrate a problem and the proposed solution, using example code that the reader then needs to read, formulate a visual "structure" in their mind, and then apply that structure to the subsequent code.
Typescript is not in any way invalid here, and as a tool when programming something that will run in the real-world, can be invaluable.
However, when writing anything you want someone to deeply comprehend, you want to use the least amount of text needed to get your point across. Adding types don't serve any purpose here. The types used are generics, which tell you nothing specific, hence the name, and the names given to the functions and object properties are enough to convey what this code is doing.
The upcoming Polonius borrow checker is supposed to solve this, but it's still in alpha...
It’s not a purely local optimization - affecting the call structure so debugging is a pain point. Which is probably why most imperative language compilers don’t bother given the lack of utility for the vast majority of code bases.
It feels like something that would need to be specified at the language spec or semantics level to make it useful rather than just making it optional for the compiler - otherwise the developer is probably just going to do the transform manually - to be safe - if stack explosion was a possibility if the compiler decided on a whim to not perform TCO.
Python famously does not have it because "Language inventor Guido van Rossum contended that stack traces are altered by tail-call elimination making debugging harder, and preferred that programmers use explicit iteration instead". https://en.wikipedia.org/wiki/Tail_call
I think you're mainly asking for heap-allocated stacks. Some languages always use the heap for stack frames instead of the native stack and can set the stack limit as high as there's memory available.
You might also want to look into stackful coroutines, which allow one to pause the execution of a recursive function and switch to another function. This can provide you with multiple call stacks, which is another reason people sometimes choose to use write explicit stacks.
Huh. Where i work, the main problem is that everyone is hell-bent on transforming every iterative function into a recursive function. If i had a pound for every recursive function called "loop" in the codebase, i could retire.
Now do breadth-first traversal. With the iterative approach, you just replace the stack with a queue. With the recursive approach, you have to make radical changes. You can make either approach look natural and elegant if you pick the right example.
The reason is that no programming language that is in widespread use has first-class support for co-recursion. In a (fictional) programming language that has this support, this is just a change from a recursive call to a co-recursive call.