Hi,
In some ML languages like Ocaml the compiler detects tail-recursions and
automatically changes it to a while loop before assembling into machine code.
Does D have this tail-recursion-optimization too?

-Jerry

Jerry wrote:
> In some ML languages like Ocaml the compiler detects tail-recursions and
> automatically changes it to a while loop before assembling into machine code.
> Does D have this tail-recursion-optimization too?

No and yes.  Tail recursion has two meanings: as a language-mandated optimisation to ensure that a valid tail recursion pattern doesn't result in a stack overflow, and as a simple optimisation pattern that a compiler might recognise.  D has the latter meaning: a compiler can apply the optimisation but it's not required to.

In a test, DMD does a tail recursion when -O is used, but not without. It didn't do tail recursion if an auto class is used as a local, so it wouldn't do it in the case of any try/finally block either and I don't know what complexity limit there is before it'll abandon the optimisation.  It really needs a tail recursion keyword to ensure that if the compiler can't tail-recurse it, then the code is considered erroneous.

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Stewart.

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