Getting started

James J. Besemer jb at
Sat Sep 28 04:24:54 EDT 2002

Adam Taylor wrote:

>Python is in the same square as Lisp (which I mentioned).  So is Perl.
>At least using this terminology... ;)

>Okay, that's true, he does define weakly-checked only in terms of
>statically checked languages, which I hadn't appreciated:
>But the clear generalization of this (it seems to me) is to define
>weakly checked languages as languages in which some unsafe operations
>are detected and some are not detected.  In other words, just delete the
>word "statically" from the last sentence in the quote above.
Exactly.  I think I said as much earlier, though not as succinctly.

>Of course, it doesn't sound like any existing languages are both
>dynamically typed and weakly checked (and I can't think of any myself):
I recall a Lisp implementation from long ago that did not distinguish 
between integers and machine addresses.  When applying a function to an 
arg list, if the function name evaluated to a number the interpreter 
blithely JSRed to that address.  This was a Feature, in that it was how 
system built-ins were linked with the higher level stuff.  User code did 
not normally do this and it was not a big issue in practice.  However it 
WAS a loophole that allowed type errors to occur, as it allowed code to 
jump to any random address in the system.  

But I think the generalization holds for most dynamic languages.



James J. Besemer		503-280-0838 voice
2727 NE Skidmore St.		503-280-0375 fax
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