[erlang-questions] Reassigning variables

Taavi Talvik <>
Tue Mar 17 22:54:04 CET 2009


On Mar 17, 2009, at 11:19 PM, Matthew Dempsky wrote:

> On Tue, Mar 17, 2009 at 1:38 PM, Justin Sheehy <>  
> wrote:
>> Single assignment is one of the biggest ways in which Erlang helps
>> reduce bugs.  Please don't try to introduce ways around it, as they
>> will make programs worse.
>
> I disagree.  There are ways that reassignment can make code easier to
> analyze, but I'm not suggesting people use reassignment in those
> cases.
>
> Similarly, Erlang doesn't support 'return', but our ad server has
> enough business logic where the code would be much simpler if it did.
> We had some code that was effectively:
>
>    if requested ad size is bad:
>        return {skip, bad_size}
>    if the game has ads disabled:
>        return {skip, disabled}
>    if the game is filtering a domain:
>        return {skip, domain_filtered}
>    return choose_ad()

Hmm..

if ad size is bad:
   throw {skip, bad_size}
if disabled:
   throw {skip, disabled}
{serve_ad, choose_ad()}

best regards,
taavi



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