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:[EMAIL PROTECTED], http://p-cos.net
Vrije Universiteit Brussel, Programming Technology Lab
Pleinlaan 2, B-1050 Brussel, Belgium
--
Pascal Costanza, mailto:[EMAIL PROTECTED], http://p-cos.net
Vrije Universiteit Brussel, Programming Technology Lab
Pleinlaan 2, B-1050 Brussel, Belgium
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