On Fri, Jan 14, 2005 at 09:47:15AM +0000, Armin Rigo wrote:
| In my opinion a user-defined class or interface mixes two notions: a
| "concept" meaningful for the programmer that the instances
| represent, and the "interface" provided to manipulate it.
...
| This suggests that only concrete objects which are expected to
| encode a *single* concept should be used for adaptation.
So, in this view of the world, the adapter from FileName to File _is_
appropriate, but the adapter from String to FileName isn't?
def checkSecurity(filename: FileName):
...
Hmm. I'd like to be able to pass in a String here, and use that
String->FileName adapter. So, there isn't a problem yet; although
String is vague in a sense, it doesn't hurt to specialize it
in the context that I have in mind.
def checkContent(file: File):
... look for well known viruses ...
def checkSecurity(filename: FileName):
... look for nasty path information ...
return checkContent(filename)
Even this is _ok_ since the conceptual jump is specified by the
programmer between the two stages. The problem happens when
one does...
checkContent("is-this-a-filename-or-is-this-content")
This is where we run into issues. When an adapter which 'specializes'
the content is used implicitly in a trasitive adaption chain.
| Note that it may be useful to be able to register some adapaters
| in "local" registeries instead of the single global one, to avoid
| all kinds of unexpected global effects.
Nice...
Best,
Clark
--
Clark C. Evans Prometheus Research, LLC.
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