[cap-talk] Abstractions that subsume capabilities

[Pierre THIERRY]

Scribit Richard Uhtenwoldt dies 11/03/2008 hora 21:04:
> 
>     def handle := <file:/etc/passwd>
>     def contents := handle.getText()
>     for line in contents.split("\n") {
>         println(line)
>     }
> 
> [...]
> 
> Since I found the E code in the E Idioms Quick Reference Card, I
> assume you all regard it as good, attack-resistant code.  But
> obviously if it does not need surgery to make it more
> attack-resistant, the Haskell code does not either.

As Kevin said, this E code relies on the lexical scope to provide some
authority, so this code wouldn't work if it was loaded as an emaker. In
this case, you'd write it this way:

--8<---- filePrinter.emaker ---------------------------------------------
pragma.syntax("0.9")

def makeFilePrinter(file, output_function) {
	def printer() {
		def contents := file.getText()
		for line in contents.split("\n") {
			output_function(line)
		}
	}
	return printer
}
--8<---------------------------------------------------------------------

Note that the authority to the device to print out to also needs to be
explicitely given.

You'd run that code this way:

? <import:filePrinter>(<file:foo.txt>, println)()

Quickly,
Pierre
-- 
nowhere.man at levallois.eu.org
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