Re: Importing

Paul Isaacs wrote:
> 
> 
> I noticed that imports done outside the interface-specification-part are 
> not dependency checked by --automake. This creates problems for first 
> time gnu pascal uses such as myself.
> 
> I started placing imports outside the interface-specification-part to 
> avoid circular dependencies and it took a while to understand that 
> --automake was no longer finding the import dependencies.

Hmm, there are bugs with automake but I am nit sure if your
description is accurate.

> I also assumed that the reason for the, rather awkward, multiple 
> interface capability was to get around the module circular dependency 
> problem. Ada resorted to the kludgy 'limited with' workaround.

multiple interface capability is specified in ISO standard.
AFAICS it is logical way to give good control over what gets
exported.  It has nothing to do with dependency problems.

> Gnu pascal seems to have resorted to the import 'in' workaround. 

That is different problem: how to map interfaces to modules and
modules to files.  At the time standard was written there were
voices that files are obsolete and source code should be
stored in databases.  Database could easily store not only
code but also mappings between interfaces and modules (and
you could retrive module source given its name).  So
apparently standard committee decided that problem of mapping
interface name to interfaces is easily solvable.

> However, having filenames in the source code does not seem to me to be a 
> good idea.

There is no need for filename in Pascal file if your build
system knows which files should be compiled.

> Would "import modulename_interfacename" work?
> 
> The first '_' character would take on special meaning but the change 
> would be 10602 specification compliant and having the module name and 
> interface name combined into one identifier would eliminate the need for 
> file names in the source code.

No.  Your proposal violates ISO-10206: underscore is legal part
of interface and module name.  And it does not solve anything:
AFAICS your modulename really means name of file containing
the module.  So you still put put filename inside Pascal
files, just instead of using nonstandard syntax (which
guarantess that there is no conflict with standard use)
you try to hijack standard syntax (which have alredy defined
and different meaning).  It is possible to modify your
proposal and be kind of compliant: namely forbid module
names containing underscores and require that interface
names always contain underscores and first part of
interface name is the same as module name.  But I see
no point: currently GPC can handle almost all Extended
Pascal module constructs (that is accepts standard code
without any changes).  Restrictions on module and
interface names while defensible from language-lawyer point
of view would mean step back.

BTW: In the past I have spent some time trying to make
better automake.  Now, I would say that automake has
one nice point: it reuses parser already present in
the compiler.  But otherwise it has serious problems.
So it would be better to have "parse for dependencies"
mode in the compiler.  Or use separate parser, as
'gp' utility is doing.

-- 
                              Waldek Hebisch

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