[squeak-dev] Objects as Booleans (was Re: Boolean over-optimization #ifTrue:/#ifFalse:)

Bert Freudenberg bert at freudenbergs.de
Wed Mar 5 11:01:07 UTC 2008

On Mar 5, 2008, at 7:52 , Lukas Renggli wrote:

>> So, the only way is to compile method without optimization of  
>> #ifTrue #ifFalse:,
>>  to make sure they do real sends?
> Just today in my blog-reader:
> http://www.cincomsmalltalk.com/userblogs/mls/blogView? 
> showComments=true&printTitle=Boolean_Objects&entry=3382109971
> This should also work in Squeak.

Hehe, very cool. It works a bit differently in Squeak, where the  
image code has to rewind the context before the jump bytecode that  
recognized the non-boolean. Attached is a little changeset that adds  
#asBoolean to various classes and overrides #mustBeBooleanIn: to use  
that, provided objectsAsBooleans has been enabled. File in, then try  

Preferences enable: #objectsAsBooleans.
#(0 1 nil #() #(a b c) 'hi' '')	collect: [:each |
	each  -> (each ifTrue: ['yes'] ifFalse: ['no'])]

#(0->'no' 1->'yes' nil->'no' #()->'no' #(#a #b #c)->'yes' 'hi'->'yes'  

Fun indeed :)

- Bert -

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