[parenscript-devel] Implicit return for function bodies

[sblist at me.com]

On 2009-11-04, at 10:33 PM, Vladimir Sedach wrote:

> I just pushed a patch that should fix that. Thanks for the bug report!

Thanks for the speedy fix!

Another trickiness around SWITCH is the behavior of fall-through
cases -- it seems like there's still a bug lurking here:

PS> (ps (lambda ()
           (switch 0
                   (1 1 break)
                   (2 2 break)
                   (3 (do-something))
                   (default 4))))
"function () {
     switch (0) {
     case 1:
         return 1;
     case 2:
         return 2;
     case 3:
         return doSomething();
     default:
         return 4;
     };
};"

I think that case 3 shouldn't return, since there was no break there
originally, so the expected behaviour is to doSomething() and then
fall-through for the return value.

- Scott

> 2009/11/4  <sblist at me.com>:
>> Hi Vladimir,
>>
>> Thanks a lot for doing this work, it'll be seriously great to have
>> implicit return!
>>
>> On 2009-11-04, at 12:57 PM, Vladimir Sedach wrote:
>>
>>> Hello,
>>>
>>> Many of you have been asking for this for a long time, and based on
>>> feedback (as well as my own experience) the lack of this feature has
>>> been the biggest cause of bugs in PS code, so it's with a bit of joy
>>> that I just pushed out a patch to add implicit returns to PS  
>>> functions
>>> (including lambdas and flet/labels) to the repository just now.  
>>> Please
>>> try it out and report any bugs you find!
>>
>> The first one I encountered was to do with the special return
>> handling for case/switch.
>>
>> 1) The return special form assumes the wrong switch/case
>> structure for these statements, it should be:
>>
>> (switch-case what &rest clauses)
>>
>> rather than:
>>
>> (switch-case what clauses)
>>
>> ...in both the destructing code and the reconstruction of the
>> clauses, having been updated with the return statement.
>>
>> 2) The return special form needs to handle break forms in
>> switch/case; rather than wrapping a break statement, it
>> should remove it and wrap the previous expression in the
>> return statement. Here's the (incorrect) output that I'm getting
>> after having fixed the first issue:
>>
>> (ps (lambda ()  (case 1 (0 1) (otherwise 2))))
>>
>> "function () {
>>    switch (1) {
>>    case 0:
>>        1;
>>        return break;
>>    default:
>>        return 2;
>>    };
>> };"
>>
>> I think we want to see:
>>
>> "function () {
>>    switch (1) {
>>    case 0:
>>        return 1;
>>    default:
>>        return 2;
>>    };
>> };"
>>
>> - Scott
>>
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>
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