[COFF] Tail-recursion was Re: [TUHS] Lorinda Cherry

[silas poulson]

Yes! That’s such as fun presentation!

For those who want the fast version, skip to 6:00 mark.

Silas

> On 23 Feb 2022, at 00:48, Will Senn <will.senn at gmail.com> wrote:
> 
> My all time favorite presentation on tail-recursion:
> 
> https://www.youtube.com/watch?v=-PX0BV9hGZY
> 
> 
> On 2/22/22 4:39 AM, Ralph Corderoy wrote:
>> Hi Otto,
>> 
>>> MacOS uses the GNU implementation which has a long standing issue with
>>> deep recursion.  It even cannot handle the tail recursive calls used
>>> here and will run out of its stack.
>> When learning dc and seeing it relied on tail calls, the first thing
>> I did was check it did tail-call elimination, and it did.  That was
>> GNU dc.
>> 
>> Trying just now, I see no growth in memory usage despite heavy CPU load
>> shown by TIME increasing.
>> 
>>     $ dc
>>     !ps u `pidof dc`
>>     USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
>>     ralph    11489  0.0  0.0   2332  1484 pts/1    S+   10:33   0:00 dc
>>     [lmx]smlmx
>>     ^C
>>     Interrupt!
>>     !ps u `pidof dc`
>>     USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
>>     ralph    11489 75.5  0.0   2332  1488 pts/1    S+   10:33   0:46 dc
>> 
>> The memory used remained at that level during the macro execution too,
>> watched from outside.
>> 
>> Do you have more detail on what GNU dc can't handle?  dc without
>> tail-call elimination is a bit crippled.
>> 
> 
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