Correct me if I’m wrong (It’s been a few years since my last comp sci course) but aren’t while loops in most languages just synaptic sugar for recursive functions. By which I mean that they compile down to the same code and aren’t functionally much different.
Zesky665
OvermindDL1
Specifically it returns the atom nil.
Depends on the back-end, if the back-end is, say LLVM, then it compiles to something that looks recursive but it bases it on blocks instead of function calls, similar concept though.
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peerreynders
Going down to assembly language a loop often has a test, conditional jump, body and unconditional jump - which really is iterative.
Also keep in mind that iteration doesn’t require a stack frame and only tail call (last call optimized) recursion can reuse a stack frame while body recursion consumes a stack frame on each call.
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OvermindDL1
LLVM has that as well except you can only reference bindings defined before, and bindings are immutable, so you have to allocate memory somewhere (stack is common) to have mutable memory. 
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sribe
Regardless of what it compiles down to, iteration is a special case, recursion is more general.
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mgwidmann
The major difference (from the developer’s point of view) between a while loop and a recursive function is that in every other language a recursive function allocates a new stack frame and therefore has a limit to how many times it can be recursively executed. In Elixir this is not true because a stack frame is not allocated due to tail recursion. That is why a while loop is not necessary in Elixir.
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sribe
In some other languages–you might be surprised how few. For starters, basically all functional languages have tail call optimization (without explicit looping constructs built in they have to), and that includes the JVM-based ones like Scala & Closure. But also C, C++, C# (actually all .NET languages because the JIT does it), Objective-C, Javascript, Kotlin…
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peerreynders
The JVM itself doesn’t TCO - so it’s up to the language to fake it.
Clojure in particular has recur to support iteration - it essentially replaces the data in a “recursion frame” before reentering the body of a loop; it’s an iterative loop based on the concept of tail recursive calls (probably one of the best examples of how iteration and recursion are two sides of the same coin).
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sribe
peerreynders
Ultimately it depends on how determined you are:
Functional Programming in Java (Pragprog)
p.123 - Chapter 7: Optimizing Recursions - Turning to Tail Recursion
https://media.pragprog.com/titles/vsjava8/code/recur/fpij/Factorial.java
https://media.pragprog.com/titles/vsjava8/code/recur/fpij/TailCall.java
https://media.pragprog.com/titles/vsjava8/code/recur/fpij/TailCalls.java
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