proper tail calls

Neil Mix nmix at pandora.com
Tue Jan 22 18:13:10 PST 2008


> The confusing traces and debugging views
> of the stack (which is not a program history!) can be mitigated.

Yes! That's my *only* concern.  (And yes, after years of debugging  
asynchronous callbacks I'm acutely aware of the difference between  
stack traces and program history.  In fact, I got so sick of it I  
hacked our test suite to store traces at key jump-off points so that  
I could capture stack from asynchronous callbacks back up to their  
originating callers.  But I digress. :P)

> But to your point, I think the party of the first part (the
> programmer who wrote code that uses tail calls) must prevail, whether
> or not they intended tail calls or expressed them explicitly. Lars
> made this point recently: unless we ban implicit PTC even when not
> elected by the programmer using explicit syntax, code will come to
> depend on PTC and we'll need it implicitly "on" everywhere. All that
> remains is the assertion.

Oh yes, Lars and Anton have convinced me that requiring explicit PTC  
is not desirable.  As I stated early on, as long as meaningful stack  
traces are doable with implicit PTC, I'll happily shush.  So consider  
me shushed.



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