[e-lang] uriGetter encoding

Thomas Leonard tal at it-innovation.soton.ac.uk
Mon Jun 28 06:12:52 PDT 2010


On Wed, 2010-06-23 at 08:32 -0700, Kevin Reid wrote:
[...]
> It is my opinion that if we're going to use URL notation, we had  
> better use URL syntax, and <file:///%20> means the file named unixly  
> "/ ", and if you want something else you had better not use angle  
> brackets and colons.
> 
> I agree that the issue of what "get" should mean is in general not  
> clear.
> 
> Hm.
> 
> Complicated option: the <a:b> notation expands to, not
>    <a>["b"]
> but
>    <a>[makeURLText("b")]
> 
> That is, we still use get/1, but label the key being looked up as  
> being not a String but a URLText, which is just a String wrapped in a  
> distinct type (which coerces to String so such distinctions can be  
> ignored when desired). Then all filesystem lookups can treat URLText  
> as %20 -> " " but treat String literally.
> 
> I rather like this idea I just invented: it is a marginal step away  
> from the hazards of untyped string data and what-escaping-level-is- 
> this. But it might be too arcane for users. Thoughts?

Well, I like it. I've used separate types for encoding strings before
and it works well to prevent subtle escaping bugs. I assume there would
be a guard for methods that need an encoded string? e.g.

? def encoded := "a b" :URIFragment
# value: URIFragment("a%20b")

? encoded :String
# value: "a b"

I was a bit worried about backwards compatibility, but maybe the
coercion fixes that. Or, we could use the syntax version to turn it on.
Coercing to a String and back would be slightly lossy (using your
example of %26 = "&"). Is that OK?


? def encoded := "&a%26b" :URIFragment
# value: URIFragment("&a%26b")

? encoded :String
# value: "&a&b"

? (encoded :String) :URIFragment
# value: URIFragment("&a&b")


-- 
Dr Thomas Leonard
IT Innovation Centre
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Hampshire SO16 7NP

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