[EMAIL PROTECTED]:
>One thing that I always think about but never get around to trying is to run
>iyacc against the Unicon grammar and have it drive a mockup of the Unicon
>virtual machine. You would wind up with an "interpreted translated
>interpreter" (or something like that) which would probably not have stellar
>performance, but might be decent and general for not-too-complex expressions.
>
>
>I wonder if anyone has attempted such a feat.
In Ruby these days, metaprogramming and DSLs are big. In order to rely
less on eval (even though Ruby has it), they've been implementing
methods for the common cases. E.g.,
v1 = 'a'
v2 = 'b'
iv1 = "@#{v1}".intern # => :@a
iv2 = "@#{v2}".intern # => :@b
class Blob; end
blob = Blob.new
blob.instance_variable_set(iv1, 1)
blob.instance_variable_set(iv2, 20*60*60*1000)
# (not really eval, just changes scope)
Blob.class_eval {
define_method(v2.intern) { instance_variable_get(iv2) }
define_method("#{v2}=".intern) {|x| instance_variable_set(iv2, x) }
}
blob.b # => 72000000
blob.b = 42
blob.b # => 42
It's not very pretty, but I think it might not be too hard to implement
similar things in Unicon.
Steve
>On Wed, 30 Aug 2006 07:07:15 -0700, Steve Wampler wrote:
>
>>
>> Lu Song wrote:
>> > Dear Everyone,
>> >
>> > I have a quesiton.
>> >
>> > Can Unicon run the Unicon source code reading from input file?
>> > for example,
>> > --------------------------------
>> > a:=1
>> > b:=20*60*60*1000
>> > --------------------------------
>> >
>> > I learned that Lisp could do it.
>>
>> As Clint reports, there is no full equivalent of Lisp's eval function
>> (One of the problems is that Unicon has a *much* richer syntax
>> than Lisp and so an embedded parser isn't as simple to implement.
>> In this day and age of huge RAM, it would certainly be doable
>> however.)
>>
>> For simple subsets of the language, such as the simple expressions
>> and assignments in your example, it's really easy to write your
>> own parser, however. I think there is at least one such solution
>> in the IPL - you might check there to see if anything suits
>> your needs.
>>
>> I also think I remember code that ran an external Icon
>> translator on source code strings and then could execute
>> the result - you might see if that's available in the IPL.
>> It's an awkward approach in some respects, but nice in
>> the fact that it doesn't require writing your own parser/
>> code generator.
>>
>> Hmmm, that might be an interesting project - extending
>> that solution (of running the Unicon icont externally) so
>> it could be invoked in a new 'thread' as a translation pipe.
>>
>> -Steve
>>
>> --
>> Steve Wampler -- [EMAIL PROTECTED]
>> The gods that smiled on your birth are now laughing out loud.
>
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