On 7 Mar 2007, at 09:39, Abdulaziz Ghuloum wrote:
>
> On Mar 7, 2007, at 2:59 AM, Thomas Lord wrote:
>
>> Abdulaziz Ghuloum wrote:
>>>
>>> Aubrey, what's this class of "pure interpreters" that you're
>>> concerned about? How do they semantically differ from say
>>> petite, csi, gsi, mzscheme, guile, gosh, rscheme, etc?
>>
>> Doesn't adding the word "semantically" to that question rather
>> miss the point?
>
> How could I miss a point when asking a question? The purpose of my
> question was to enquire, not to miss or make a point. If you think
> the question was invalid, then please explain.
>
>
>> Did anyone deny that the current R6 draft could be implemented,
>> portably,
>> atop any R5 implementation, including SCM?
>
> That's pretty close to what I understood from Aubrey's opening
> sentence:
>
>> By requiring phased processing of libraries, R5.92RS has
>> disenfranchised "pure interpreters", apparently for the sake of
>> macros.
>
> And acccording to my dictionary (English is not my first language):
> disenfranchise: deprive (someone) of a right or privilege
>
> So, how could R6RS disenfranchise pure interpreters, and at the
> same time, be implemented atop these same interpreters?
The terms "compiler" and "interpreter" are not well-defined. But
AFAICT, a compiler typically works in two phases: A translation from
one representation to another one, where the latter is typically a
representation that can be executed by some interpreter (for example,
a CPU).
An interpreter typically works in one phase: It evaluates expressions
one by one without doing any sort of whole-program analysis.
Interpreters are interesting because they sometimes have better
performance characteristics than compilers. Especially when code is
loaded or generated on demand at runtime, a compilation step may
incur a much larger overhead than "pure" interpretation. For example,
this is the case when the loaded or generated code is only executed
once or just a few times.
This is, BTW, one of the reasons why "modern" virtual machines, like
those for Java, Smalltalk or Self, are so efficient: They simply
defer compilation until there is enough evidence that certain
hotspots actually benefit from an extra compilation step.
Pascal
--
Pascal Costanza, mailto:pc_at_p-cos.net, http://p-cos.net
Vrije Universiteit Brussel, Programming Technology Lab
Pleinlaan 2, B-1050 Brussel, Belgium
--
Pascal Costanza, mailto:pc_at_p-cos.net, http://p-cos.net
Vrije Universiteit Brussel, Programming Technology Lab
Pleinlaan 2, B-1050 Brussel, Belgium
Received on Wed Mar 07 2007 - 05:13:47 UTC