<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">2013/10/31 Sven Barth <span dir="ltr"><<a href="mailto:pascaldragon@googlemail.com" target="_blank">pascaldragon@googlemail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>Am 31.10.2013 12:38, schrieb Frederic
Da Vitoria:<br>
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<div class="gmail_quote">2013/10/31 Sven Barth <span dir="ltr"><<a href="mailto:pascaldragon@googlemail.com" target="_blank">pascaldragon@googlemail.com</a>></span><br>
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<div>Am 31.10.2013 02:45, schrieb Xiangrong Fang:<br>
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<div style="font-family:courier new,monospace"><span style="font-family:arial">2013/10/30 Jonas
Maebe </span><span dir="ltr" style="font-family:arial"><<a href="mailto:jonas.maebe@elis.ugent.be" target="_blank">jonas.maebe@elis.ugent.be</a>></span><br>
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This is not equivalent. A private type
declaration in a class adds a new
identifier that is visible inside that
class. You then use it, still in that
class, to declare the return type of a
function. Next, in a scope where that type
identifier is no longer visible, you call
the function.<br>
<br>
My example is a complete match to that
scenario as far as identifier visibility
is concerned (you use a type in a scope
where it is visible to declare a function
return type, and then call the function in
a scope where it is not visible). In your
example, the type is not visible in the
place where the function is declared but
only where it is defined
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<div>This is logically WRONG. Because to
the machine, any function return value
can be seen as an array of bytes, for
example, a pointer is array[0..3] of
Byte on a 32-bit machine. The purpose
of type system is to explain what these
bytes stands for. So, if a type is
out-of-scope, how do you interpret the
data? </div>
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<div>The current "delphi compatible"
implementation IS using the type
information to compile the program, i.e.
although it is not visible, it is indeed
used by the compile, which, in my
opinion, violates visibility rules.</div>
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<div>Standing on your view point, if a
type is no longer visible, but a
variable (function return value) of that
type is in current scope, and understood
by the program, this means, this value
itself carries type information! Is is
kind of meta data available in Pascal?
If so, I think RTTI should work for ANY
kind of primitive data types.</div>
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For unit interfaces there is indeed the point that if
unit A uses unit B then the program which uses unit A
will be able to access types used by unit A. E.g.:<br>
<br>
=== unit A ===<br>
<br>
unit A;<br>
<br>
interface<br>
<br>
type<br>
TTest = class<br>
procedure Test;<br>
end;<br>
<br>
implementation<br>
<br>
procedure TTest.Test;<br>
begin<br>
Writeln('Foobar');<br>
end;<br>
<br>
end.<br>
<br>
=== unit A ===<br>
<br>
=== unit B ===<br>
<br>
unit B;<br>
<br>
interface<br>
<br>
uses<br>
A;<br>
<br>
function SomeTest: TTest;<br>
<br>
implementation<br>
<br>
function SomeTest: TTest;<br>
begin<br>
Result := TTest.Create;<br>
end;<br>
<br>
end.<br>
<br>
=== unit B ===<br>
<br>
=== program ===<br>
<br>
program test;<br>
<br>
uses<br>
B;<br>
<br>
begin<br>
// there won't be an error here<br>
SomeTest.Test;<br>
end.<br>
<br>
=== program ===<br>
<br>
It's this way at least since Turbo Pascal (though
without classes then ;) ).<br>
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<div class="gmail_extra">Yes, I agree this is the TP/Delphi way,
and as such should be kept at least in DELPHI mode. But is
this really good? Doesn't this contradict the Pascal
philosophy? Borland did a few questionable things (look at how
you used the semicolons in you examples above ;-) ), and it
took some decisions when implementing units. But how is this
handled in Modula?<br clear="all">
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Undoing this even for only non-TP/Delphi modes would mean adjusting
very much code out there. So no, this is how Object Pascal works.<br>
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</blockquote></div><br></div><div class="gmail_extra">Ah, you mean that this is too much intricately mixed with the compiler code and it would be much too much work to change? OK, this I understand :-)<br clear="all"></div>
<div class="gmail_extra"><br>-- <br>Frederic Da Vitoria<br>(davitof)<br><br>Membre de l'April - « promouvoir et défendre le logiciel libre » - <a href="http://www.april.org" target="_blank">http://www.april.org</a><br>
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