Object>>caseOf: (was Re: [Q] Enum style Object?)
ian.piumarta at inria.fr
Wed Feb 19 13:56:47 UTC 2003
On Wed, 19 Feb 2003 tblanchard at mac.com wrote:
> On Wednesday, February 19, 2003, at 11:58 AM, Marco Paga wrote:
> > Hi all.
> > Using switch/case/many if's is in OO languages the sign that something
> > is going very wrong. The Object>>caseOf: /otherwise: should get banned
> > from the image.
> You know, ordinarily I agree with you - but its a terribly handy thing
> when parsing input - read a character and then caseOf: do the right
> thing with it.
Take a look at how the Scanner works. It does "the right thing". An
Array of 256 symbols indexed by the initial character in each token to
provide a selector for #perform: that invokes the method responsible for
parsing the rest of the token. (The selectors in question all start with
> So I think banning it from the image is a bit strong.
...there are times when the input is not neatly represented by something
you can turn into a cardinal within a smallish range, from which to build
a dispatch table. #caseOf: solves this one way, although another way
would be to replace Array in the above solution with [Identity]Dictionary.
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