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Invoking return through a function?

Rhodri James rhodri at kynesim.co.uk
Mon Oct 30 10:27:04 EDT 2017 
On 29/10/17 16:45, Alberto Riva wrote:
> On 10/29/2017 11:13 AM, bartc wrote:
>>
>> (What the OP wants was also proposed a few weeks back in comp.lang.c. 
>> But that was only within nested functions, so if H is inside G, and G 
>> is inside F, then a 'returnall' from H would return directly directly 
>> from F. Apparently Lisp allows this...)
> 
> Well, not directly, but it can be simulated with the condition system 
> (equivalent to try/except) or with throw/catch, which is similar but 
> doesn't use exceptions.
> 
> But my point was that in Lisp you don't need to do this, because you can 
> write a macro that expands into a return *in place*, without calling a 
> separate function, and this eliminates the problem entirely. Since 
> Python doesn't have macros I was looking for the next-best solution, but 
> there doesn't seem to be one. Oh, well...

You can do the same in C.  I've had the displeasure of trying to 
maintain such code.  It was near-unreadable, because it constantly broke 
your expectations of what the code flow *could* be.  The fact that 
something that could return from the middle of your function without the 
slightest indication was a rich source of bugs.

(I didn't have to tell my boss to up our rates for dealing with this 
code.  It took several days to do the work anyway, which was punishment 
enough at our rates.)

-- 
Rhodri James *-* Kynesim Ltd
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