On 18 May 2008, at 19:55, immanuel litzroth wrote:
So the C language itself does not
have any #include directive.
The C language standard is available at:
http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf
You'll see all the preprocessing directives explained there and no
mention of a separate preprocessor program.
Sure: it just defines the two languages, without explicitly
mentioning their grammar sentence symbols. So it is formally
impossible to deduce it from the standards alone. Somebody pointed
this out to me. The C++ standardization committee felt this was clear
enough, since the standard does not include a formal grammar, but jut
an informal description of it.
The introduction does say: "A C program need not all be translated
at the same time".
This refers to the C/C++ grammar sentence symbol called "translation-
unit". Translation units can be compiled separately at different
times and later linked together using the C linker.
This is probably just to define the language semantics.
That's my point, semantically the inclusion models are the same.
It just describes the module effect of name separation.
Haskell does not define how modules are mapped to files, how they
are searched for...
The point is to not do that, but keep the information within the
language, so that a better analysis of dependencies can be done.
...and how to "figure out" what to include in a compilation. These
are implementation issues.
In Haskell, you really only need to tell what you need, not worrying
how it should be included syntactically (though the location of the
module must somehow be given)). In each module one tells what other
modules it may depend on, and then Haskell figures out out to link
them together. This is different from C/C++ where one by hand has to
make the file inclusions i the right order and put in guards to that
files are not include more than once, so that hopefully a series of
translation units are created which can be linked together by the C
linker.
Hans
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