Recursive calls and stack

[Neil Cerutti]

On 2007-02-15, Gabriel Genellina <gagsl-py at yahoo.com.ar> wrote:
> En Thu, 15 Feb 2007 13:37:19 -0300, Neil Cerutti <horpner at yahoo.com>  
> escribió:
>
>> On 2007-02-15, Gabriel Genellina <gagsl-py at yahoo.com.ar> wrote:
>>> En Wed, 14 Feb 2007 10:41:53 -0300, Neil Cerutti <horpner at yahoo.com>
>>> escribió:
>>>> So the effect is that mutual recursion isn't actually any
>>>> harder.
>>>
>>> But some kind of language support is required in this case. At
>>> least I  don't know how to handle mutual recursion (apart from
>>> inlining one  function inside the other...). But I'm certainly
>>> not a "program  transformation guru" (neither a novice!) so I
>>> would not be surprised if  someone says it can be done...
>>
>> What happens (using the model of an imaginary virtual machine,
>> perhaps like the Python interpreter) is the following.
>>
>> A normal function call pushes a call-frame onto a stack. The
>> call-frame contains information necessary for returning from the
>> function, and usually a place to store its local variables and
>> parameters.
>>
>> A function called in "tail" position simply overwrites the
>> current call-frame with the new one instead of pushing it onto
>> the stack.
>
> This is the "kind of language support" menctioned. For tail
> recursion you  don't require that support.

I'm not sure what you mean. The above support is enough for tail
recursion, mutual recursion, and any other tail call to be
"optimized."

-- 
Neil Cerutti