Scala does tail recursion optimisation at compile-time, as other posters have said. That is, a tail recursive function is transformed into a loop by the compiler (a method invoke is transformed into a jump), as can be seen from the stack trace when running a tail recursive function. Try the following snippet: def boom(n: Int): … Read more
C# compiler does not give you any guarantees about tail-call optimizations because C# programs usually use loops and so they do not rely on the tail-call optimizations. So, in C#, this is simply a JIT optimization that may or may not happen (and you cannot rely on it). F# compiler is designed to handle functional … Read more
First, let’s translate the clauses into something more understandable: append([], List, List) :- !. can be written append([], List2, Result) :- Result = List2, !. and append([H|L1], List2, [H|L3]) :- append(L1, List2, L3). can be written append(List1, List2, Result) :- List1 = [Head1 | Tail1], Result = [HeadR | TailR], Head1 = HeadR, append(Tail1, List2, … Read more
Start with a simple task, like mapping items from ‘a to ‘b in a list. We want to write a function which has the signature val map: (‘a -> ‘b) -> ‘a list -> ‘b list Where map (fun x -> x * 2) [1;2;3;4;5] == [2;4;6;8;10] Start with non-tail recursive version: let rec map … Read more
The ECMAScript 4 specification was originally going to add support for TCO, but it was dropped: No more tail calls in JavaScript? As far as I know, no widely-available implementations of JavaScript currently do automatic TCO. This may be of use to you, though: Tail Call Optimization Essentially, using the accumulator pattern accomplish the same … Read more
Welcome to the world of lazy evaluation. When you think about it in terms of strict evaluation, foldl looks “good” and foldr looks “bad” because foldl is tail recursive, but foldr would have to build a tower in the stack so it can process the last item first. However, lazy evaluation turns the tables. Take, … Read more
Let’s use the example code from the other question. Compile it, but tell gcc not to assemble: gcc -std=c99 -S -O2 test.c Now let’s look at the _atoi function in the resultant test.s file (gcc 4.0.1 on Mac OS 10.5): .text .align 4,0×90 _atoi: pushl %ebp testl %eax, %eax movl %esp, %ebp movl %eax, %ecx … Read more
Update: As of January 1, 2020 Safari is the only browser that supports tail call optimization. The chromium team explicitly states that Tail Call Optimization is not under active development and can be tracked here. The implementation for Firefox can be tracked here Original Post Yes, ES2015 offers tail call optimization in strict mode. Dr. … Read more
You have three (or so) options to break out of loops. Suppose you want to sum numbers until the total is greater than 1000. You try var sum = 0 for (i <- 0 to 1000) sum += i except you want to stop when (sum > 1000). What to do? There are several options. … Read more
A simple tail recursive function: unsigned int f( unsigned int a ) { if ( a == 0 ) { return a; } return f( a – 1 ); // tail recursion } Tail recursion is basically when: there is only a single recursive call that call is the last statement in the function And … Read more