Gpc October 1997

gpc@gnu.de

31 participants
158 discussions

Re: Questing on String
by Peter Gerwinski 25 Oct '97

25 Oct '97

Hello, Thomas; hello, everybody! According to Thomas Tan: > > How does writeln(astring) work, I am not sure whether I understand your question ... To use `writeln', just do writeln ( MyIntegerValue : 6, MyRealValue : 10 : 4, MyStringValue : 7 ); to get 42 3.1415 Hallo! or writeln ( 'Answer = ', MyIntegerValue ); to get Answer = 42 If you want to know how `writeln' works internally, please look at the GPC source, file `rts.c', and in the subdirectory `rts' at the files `rts-write.c' and `rts-wrtinc.c'. If you have more questions about that, please post them on this list. > is the string null terminating? No, but GPC has an additional string type `CString' (or `PChar' for BP compatibility) which *is* null-terminated. If you have, for example, a null-terminated string you want to pass to an external function that wants to have such a string as a parameter (this holds for many external functions written in C), you can use `CString' as follows: Program Environment; (*$X+*) (* Enable "extended syntax" if you want to use `CString' *) Function SetEnv ( Name, Value: CString; overwrite: Integer ): Integer; C; Function GetEnv ( Name: CString ): CString; C; Var S: CString; begin SetEnv ( 'TEST_ENV', 'OK', 1 ); S:= GetEnv ( 'TEST_ENV' ); writeln ( S ); end. > If so, what is the character of null? Not too surprisingly, it is `chr ( 0 )' or `#0'. :-) For `CString'. GPC's native `String' is *not* null-terminated. And to answer your implicit question about GPC string internals: GPC's native `String' is a special case of a "schema type". It looks like a record internally: Type String ( n: Integer ) = record Capacity, length: Integer; (* 8 bytes *) data: packed array [ 1..n ] of Char; (* n bytes *) end (* String *); (* Remark: The above is a perfectly valid type declaration in GNU Pascal or any other compiler that supports Extended Pascal's schema types. It is, however, not identically the same as GPC's `String' since the built-in string functions only work on the built-in string type, but it has the same structure in memory. *) When you declare a string variable with "Var Foo: String ( 42 )" (* Now you see where the round parentheses come from. ;*), the "record field" `Capacity' gets the value 42 assigned, while `length' and `data' remain undefined until you assign a value to the string. You can access a string's capacity with `Foo.capacity' just like a record field. For dynamical allocation of strings, you can define "Type StringPtr = ^String" *without* a specified capacity and then give it when `New'ing the variable. Program Test; Type StringPtr = ^String; Var Foo: StringPtr; begin New ( Foo, 1042 ); (* allocate a String of maximum length 1042 *) Foo^:= 'Hello, world!'; writeln ( Foo^.Capacity ); (* yields "1024" *) writeln ( Foo^ ); (* yields "Hello, world!" *) Dispose ( Foo ); end. In addition to these features of Extended Pascal, GPC supports the following extensions: Type StringPtr = ^String; Var Foo: StringPtr; Foo:= @'Hello, world!'; (* let `Foo' point to a string constant *) Foo:= New ( StringPtr, 42 ); (* let `New' act as a function *) If you want to contribute to the GNU Pascal project, feel free to improve the existing documentation by adding the things I wrote above (and more;-). If you do so, please do not forget to post to this list what you are doing so you can coordinate with others who are currently working on the same field. Hope this helps, Peter Dipl.-Phys. Peter Gerwinski, Essen, Germany, free physicist and programmer peter.gerwinski(a)uni-essen.de - http://home.pages.de/~peter.gerwinski/ [971005] maintainer GNU Pascal [971001] - http://home.pages.de/~gnu-pascal/ [971005]

1 0

Objects question
by Thomas_Tan＠fc.choate.edu 25 Oct '97

25 Oct '97

When I took a look at objects.pas in the \test\borland_\ directory (a copy below), a few questions raise to mind. 1. Does the character c have to be desposed in the destructor? If so, is char (0) a null character? 2. If there are variables (character, arrays ,strings, etc) in a function in an object, do they have to be manually deleted? If so, how would I erase each one of them? 3. Is there such a thing as a pointer to a function? Thanks Tom Program Objects;(* Bug fixed: objects only worked in units, not in programs. *)Type ParentPtr = ^ParentObj; ChildPtr = ^ChildObj;ParentObj = object Constructor Init; Destructor Fini; Procedure O; c: Char; (* GNU extension: mixing of fields and methods *) Procedure K; virtual;end (* ParentObj *);ChildObj = object ( ParentObj ) (* Bug fixed: no dummy variable needed here. *) Procedure O; Procedure K; virtual;end (* ChildObj *);Var MyObject: ParentPtr;Constructor ParentObj.Init;begin (* ParentObj.Init *) c:= 'K';end (* ParentObj.Init *);Destructor ParentObj.Fini;begin (* ParentObj.Fini *) c:= chr ( 0 );end (* ParentObj.Fini *);Procedure ParentObj.O;begin (* ParentObj.O *) write ( 'O' );end (* ParentObj.O *);Procedure ParentObj.K;begin (* ParentObj.K *) write ( 'y' );end (* ParentObj.K *);Procedure ChildObj.O;begin (* ChildObj.O *) write ( 'x' );end (* ChildObj.O *);Procedure ChildObj.K;begin (* ChildObj.K *) inherited K; writeln ( chr ( 8 ) + c );end (* ChildObj.K *);begin MyObject:= New ( ChildPtr, Init ); with MyObject^ do begin O; K; end (* with *); Dispose ( MyObject, Fini );end. ------------------------------------------------------ This message sent using the FirstClass SMTP/NNTP Gateway. From: Choate Rosemary Hall 333 Christian St. Wallingford, CT. 06492

1 0

Questing on String
by Thomas_Tan＠fc.choate.edu 25 Oct '97

25 Oct '97

How does writeln(astring) work, is the string null terminating? If so, what is the character of null? ------------------------------------------------------ This message sent using the FirstClass SMTP/NNTP Gateway. From: Choate Rosemary Hall 333 Christian St. Wallingford, CT. 06492

1 0

Re: GPC question
by Jesper Lund 24 Oct '97

24 Oct '97

Tom: >Thank you again. Is there a list of all the built-in functions somewhere(as well >as all the interfaces)? One more thing, I cannot pass a string[255] variable to >a function or return a string[255] from a function. Is this a bug? >Thanks again. >Tom > First of all: please post general questions about GPC to the GPC list <gpc(a)hut.fi>, and not to me directly. GPC is under development, and so is the documentation. Therefore, AFAIK, there is no *complete* list of the built-in functions. However, GPC is reasonably compatible with Borland Pascal, and the degree of compatibility is increasing day by day, as new versions are released. BTW, do you use the last beta release, dates Oct 1, 1997? If not, get it from the GPC homepage. Regarding your second question, I think you need to define a string type, like type str255 = string [255]; function Foo : str255; begin Foo = 'Foo'; end; This should work. Note that 'string' has a different meaning in GPC than in Borland Pascal. To avoid unexpected effects, use strings of fixed size, such as my str255 -- or study the GPC documentation about "variable length strings". Best wishes, Jesper Lund

1 0

GPC question
by Thomas_Tan＠fc.choate.edu 24 Oct '97

24 Oct '97

Hi, I am looking for a function which returns the current time or date, is there one built in, if so, what do I put after the USES? Tom ------------------------------------------------------ This message sent using the FirstClass SMTP/NNTP Gateway. From: Choate Rosemary Hall 333 Christian St. Wallingford, CT. 06492

2 1

Bug report
by The African Chief 24 Oct '97

24 Oct '97

Hi all, I have found a bug in the new beta. If you export a function in one unit, and then in another unit that uses that first unit, you have the same function (but only in the implementation section), you get a compiler error. This result; [----] two.pas:9: warning: static declaration for `Positive' follows non-static two.pas: In function `Positive': two.pas:10: undeclared identifier `I' (first use this function) two.pas:10: (Each undeclared identifier is reported only once two.pas:10: for each function it appears in.) [----] is produced by these two units; unit one; interface function positive(var i:integer):boolean; implementation function positive(var i:integer):boolean; begin positive := i > 0; end; end. {//} unit two; interface uses one; function negative(var i:integer):boolean; function neutral(var i:integer):boolean; implementation function positive(var i:integer):boolean; begin positive := i > 0; end; function neutral(var i:integer):boolean; begin neutral := i = 0; end; function negative(var i:integer):boolean; begin negative := i < 0; end; end. {////} Best regards, The Chief -------- Dr. Abimbola A. Olowofoyeku (The African Chief) Email: laa12(a)keele.ac.uk Author of: Chief's Installer Pro 4.01 for Win16 and Win32: Winner of PC PLUS Magazine Gold Award (April 1995 U.K. edition) http://ourworld.compuserve.com/homepages/African_Chief/ ftp://ftp.demon.co.uk/pub/ibmpc/win3/apps/chief/pro/chief401.zip

1 0

Re: Pointer arithmetics, automatic `uses'
by Peter Gerwinski 24 Oct '97

24 Oct '97

According to The African Chief: > > This is getting very interesting :-) We now have many different > versions of FillChar! Which should I use? One that works, and among those the fastest one. > > BTW, pointer arithmetics ... should GPC allow constructions like > > > > (*$X+*) > > > > Var > > p, q: ^Char; > > > > p:= q + 42; > > > > or only > > > > p:= succ ( q, 42 ); ? > > > > Personally, I would prefer to allow only the second (Pointer being an > > ordinal type) and to consider the first (Pointer + Integer) an error, > > but it's technically easier to allow both, so I ask before I remove a > > bug somebody might consider a feature. ;-) > > Personally, I would keep both. I am not in favour of imposing > restrictions on programmers, unless it is for their own good! I > suppose we could assume that anyone who wants to use the first > permutation knows what he/she is doing. One "pro" for keeping both is that "Pointer - Pointer" yields an Integer, so "Pointer + Integer" should work too and act as a reverse of the first. > PS: - another point entirely; is there a switch that will enable > a particular unit (in this case SYSTEM.PAS) to be used > automatically, without putting it manually in the USES clause of > every source file? I am looking for something like > > "--auto-use=xxx.pas,yyy.pas,f:\gpc\zzz.pas", > > which I can then use from the command line, or put into to > GPCC.CFG file. This is planned, and `--auto-use=...' is a good suggestion for the name. Okay with everybody? (Or perhaps `--auto-uses=...'? Or just `--uses=...'?) Peter Dipl.-Phys. Peter Gerwinski, Essen, Germany, free physicist and programmer peter.gerwinski(a)uni-essen.de - http://home.pages.de/~peter.gerwinski/ [971005] maintainer GNU Pascal [971001] - http://home.pages.de/~gnu-pascal/ [971005]

2 1

Re: BPCOMPAT v1.10 -released!
by Frank Heckenbach 24 Oct '97

24 Oct '97

The African Chief wrote: > > For the other type declarations, I suggest you use the more modern GPC integer > > types (as invented some months ago), rather than the old style __modifiers__. > > (Also for real types.) > > Frankly, I am totally lost as far as that is concerned. Is there > any authoritative list of all the numerical types? I assume Peter's description in the announcement of GPC-970624 in <199706250026.CAA18851(a)agnes.dida.physik.uni-essen.de> can be considered authoritative: --- BEGIN QUOTE --- * GPC has new integer types now. Below is a table with their sizes in bits and their equivalents in (GNU) C. The size is the same for all platforms I have access to, but I am not sure whether this will always and everywhere be the case. However, compatibility to GNU C is guaranteed to work to the extend of the GNU GPL. ;-) The `*Int' types are signed (integer), the `*Card' types unsigned (cardinal numbers). The `*Word' types are unsigned, too, but should be thought of having undefined sign; they are intended to be used where signedness does not matter. Bits Signed Unsigned undefined (GNU) C equivalent 8 ByteInt ByteCard Byte [signed|unsigned] char 16 ShortInt ShortCard ShortWord short [unsigned] int 32 Integer Cardinal Word [unsigned] int 32 MedInt MedCard MedWord long [unsigned] int 64 LongInt LongCard LongWord long long [unsigned] int 64 LongestInt LongestCard LongestWord long long [unsigned] int In addition, you can define the number of bits for `Integer', `Cardinal', and `Word' types by putting it in parentheses, Type Int16 = Integer ( 16 ); (* 16 bits *) Unsigned17 = Cardinal ( 17 ); (* 17 bits; stored in 32 bits *) (* except when in packed arrays *) (* and records (or on machines *) (* with 17-bit registers:-). *) Answer = Word ( 42 ); (* Stored in 64 bits *) The size is rounded up to the next unit the machine can access, usually a power of 2 with 8 bits being the smallest possible size. * Subrange types can be packed now: Type Foo: -12..127; (* Takes 4 bytes (fast access) *) Bar: packed -12..127; (* Takes 1 byte (saves memory) *) --- END QUOTE --- So I suppose, for "portable" BP compatibility, the "(n)" variants are best suited: type ShortInt = Integer (8); Byte = Cardinal (8); Word = Cardinal (16); LongInt = Integer (32); Comp = Integer (64); Integer = Integer (16); const MaxInt = $7FFF; {@@ better: High(Integer) as soon as High will be built-in} MaxLongInt = $7FFFFFFF; {@@ High(LongInt)} For the C integers, you can use the table above (e.g. "long = MedInt"). Single, Double and Extended are built-in already. Real can be left as it is (which is either Single or Double, dependent on a swicth, IIRC), or generally defined to Double, I don't know -- it's not 100% the same as in BP, anyway... Pointer is also built-in, BTW. > > Procedures assgined to procedural variables can be in the main program now, > > so you can remove this comment for ExitProc. > > I am still having some problems with this. Can you show us an example where this is a problem, so it can be fixed? Another detail concerning ExitProc: There is a little difference between how BP's and GPC's system.pas handle them. BP sets them to NIL before calling an ExitProc. The effect is, when an exit proc "forgets" to assign the next one to ExitProc, the chain will abort rather than infinitely calling the same exit proc. I think the following would be 100% compatible: to end do begin var Tmp: Pointer; while ExitProc<>nil do begin InOutRes := 0; Tmp := ExitProc; ExitProc := NIL; PProcedure (Tmp)^ end end; The following program demonstrates the effect: program x; {$ifdef __GPC__}uses system;{$else}{$f+}{$endif} var Next1, Next2: Pointer; procedure e1; begin ExitProc:=Next1; Writeln('ExitProc1') end; procedure e2; begin (* ExitProc:=Next2; *) Writeln('ExitProc2') end; begin Next1 := ExitProc; ExitProc := @e1; Next2 := ExitProc; ExitProc := @e2; end. > > Assign is built-in now, so you can remove it from system.pas. > > Done. Does it now cater for all file types? Currently only Text files and typed files (which are the same internally in GPC). Untyped files are very different (as declared in system.pas), a fact I'm not very happy with. I think, they will be changed to be like typed files, but probably not until GPC 2.1... > Basically, DOS is a beast of a unit to implement - especially the > Findxxx functions. There are still problems with a "DIR" listing > using these functions if there are .EXE files in the list. There > are all sorts of other problems as well. I don't think it will > ever be portable. I have given up on the DOS unit. If someone > else wants to do it, please feel free! I see the problems. I suppose, *if* we can make a C header to Pascal translator (which is a very difficult task), we can make use of some (hopefully portable) C system functions to emulate most of Dos (though this will probably require some amount of additional Pascal code)... I think this is a task to face after 2.1... > > Unit Printer: > > > > can be written now (at least for DJGPP). > > Done! BTW: Do you close the printer file it in a "to end do" statement? BP, AFAIK, doesn't do so, but it's better to do. > Ok - thanks. I note Frank's comments - and so I will leave "Val" > alone. > Frank - will your "Val" procedure deal with reals as well? Yes, there are different versions for the 10 basic integer types and the 3 real types (shortreal, real, longreal), which will all be "overloaded" to the name "Val". Integer subranges should also work then, bit fields (fields of packed records/arrays that are not complete bytes) might not work until some time later... > Yes, it is. This is how it is implemented in "AddNull", which was > in the strings unit before, but I have now moved it into the > system unit, since the system unit also uses that functionality. > > Any thoughts on whether the system unit should now export this > AddNull function so that it can be available globally? This would > introduce something which is not in the BP system unit. I'm not sure if it should, since something like this will be built-in later, so programs shouldn't rely on the version in system.pas. Besides, I think, the name "AddNull" could be unclear or ambiguous (though I doubt someone would write a procedure of this name operating on numbers... ;-). I'd rather call it something like "Str2CString" or so... > PS: - another point entirely; is there a switch that will enable > a particular unit (in this case SYSTEM.PAS) to be used > automatically, without putting it manually in the USES clause of > every source file? I am looking for something like > > "--auto-use=xxx.pas,yyy.pas,f:\gpc\zzz.pas", > > which I can then use from the command line, or put into to > GPCC.CFG file. I agree, I'd also like to have this -- especially for the system unit. It's planned to make this, perhaps even until 2.1. -- Frank Heckenbach, Erlangen, Germany heckenb(a)mi.uni-erlangen.de http://home.pages.de/~fjf/links.htm

2 1

Re: Error while compiling simple Pascal-Program
by Peter Gerwinski 24 Oct '97

24 Oct '97

According to Christian Bockermann: > > I have installed version 2.3 of the gnu assembler (gas) but now I get an > error when compiling my pograms. I wrote a little test program like this : > > program test; > var ch : char; > begin > ch:='x'; > writeln(ch); > end. This program compiles well on my box. (Uh - I hate non-reproducable errors!)-: I am using version 2.8.1 of the GNU assembler. Maybe that's the problem? If you upgrade and the error is still there, it could be a good idea to run `gpc' with the options `-v --automake=-v'. Hope this helps, Peter Dipl.-Phys. Peter Gerwinski, Essen, Germany, free physicist and programmer peter.gerwinski(a)uni-essen.de - http://home.pages.de/~peter.gerwinski/ [971005] maintainer GNU Pascal [971001] - http://home.pages.de/~gnu-pascal/ [971005]

1 0

Integer types (was: BPCOMPAT v1.10 -released!)
by Peter Gerwinski 24 Oct '97

24 Oct '97

According to The African Chief: > > > For the other type declarations, I suggest you use the more modern GPC integer > > types (as invented some months ago), rather than the old style __modifiers__. > > (Also for real types.) > > Frankly, I am totally lost as far as that is concerned. Is there > any authoritative list of all the numerical types? It's in the GPC info documentation, section "Integer types", and there is also an Info node for each type. Hope this helps, Peter Dipl.-Phys. Peter Gerwinski, Essen, Germany, free physicist and programmer peter.gerwinski(a)uni-essen.de - http://home.pages.de/~peter.gerwinski/ [971005] maintainer GNU Pascal [971001] - http://home.pages.de/~gnu-pascal/ [971005]

1 0

← Newer
1
2
3
4
5
6
7
8
9
...
16
Older →

Jump to page:

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

Gpc October 1997