Re: how to design a replacement for C++

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 31 Jul 2010 06:38:19 -0700 (PDT)
Message-ID:
<6d56ce9b-8670-4663-bb7c-816539f2bc7d@u26g2000yqu.googlegroups.com>
On Jul 30, 6:49 pm, Keith H Duggar <dug...@alum.mit.edu> wrote:

On Jul 30, 1:31 pm, Joshua Maurice <joshuamaur...@gmail.com> wrote:


    [...]

But the argument concerned more the developer, who modifies one
small implementation detail (in a source file in C++), then does
make. With Java, every class which uses the modified class will
be recompiled. With C++, only the one source file will be
recompiled.


The system could be improved so that if it detects that the "external
visible class file exported 'interface' " has not changed since last
compile, that is it has the same list of functions and fields with the
same types and names, then it doesn't need to recompile "clients" aka
class files which use that type name. If you just modify the internals
of a Java function, then the class "exported interface" will not
change, so there is no need to recompile "clients", but if you add,
remove, or modify the name or type of a field or function, then you do
have to recompile clients. This is exactly analogous to headers and
cpp files for C++. You just need some not-make-based logic to deal
with it.


The problem is that such systems require parsing of the file
and language specific analysis of the file. And that analysis
must examine not only the current contents but some previously
known contents as well. All that is significantly more complex
and costly than simply checking a timestamp, checksum, etc.


They require meta-information of some sort. If the compiler
collaborates, it could easily generate that meta-information
when compiling. And evaluating that meta-information should
actually cost less than checking a checksum (but not a time
stamp).

--
James Kanze

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