|Just another Perl shrine|
Re^7: Nobody Expects the Agile Imposition (Part VI): Architectureby BrowserUk (Pope)
|on Jan 23, 2011 at 23:09 UTC||Need Help??|
Yes, the definition of what "rewrite" means is open to interpretation. FWIW, I was following the spirit of the definition used by Joel Spolsky
I agree that the term is subject to interpretation, but I think using NT as an example of a "rewrite" (of 3.1 or 95), misses the spirit of Joel's definition.
There are 3 parts to any piece of software development
I think Joel Spolsky's example of the Netscape browser is a good example of a re-write because both version 4 and version 6 were effectively written to meet the same design: HTML rendered to a SDI GUI. My reading of his point is that whilst Netscape 4 had evolved into a spaghetti architecture, much of code underlying the rendering could have been retained.
I cannot comment on the Perl 4/5 transition as I never used 4 and have never looked at the implementation.
For Perl 5/6. Whilst the language retains the flavour of Perl, it is sufficiently different to consider that the design has changed. The complete segregation of the parsing & AST generation from the interpreter run-loop, means that the architecture is radically different. And the fact that almost nothing of the Perl 5 implementation could be reused--even if it was desired--means that the implementation has to be completely new. As such, I would say that it is not a re-write, but rather a substantial re-design; and radical re-architecture; and a completely new implementation.
And getting back to NT/95/3.1. 3.1 was a single user, single address-space, cooperative multi-tasking OS with no security, and no protection or differentiation between different tasks, nor even between application and kernel level code.
NT was designed from the ground up with sophisticated--many would say overcomplicated--security and right management; pre-emptive multi-tasking; strict segregation of kernel (ring 0) and user (ring 3) code; protected virtual address spaces; blah blah.
I think that as an example for your purposes, its inclusion actually weakens your argument.
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