Re: [fpc-devel] Could FPC add the PLM based construct?
Micha Nelissen ha scritto: Giuliano Colla wrote: Micha Nelissen ha scritto: Giuliano Colla wrote: With absolute you need a) to declare an extra type (PByte, or Declaring an extra type is one of those things that make Pascal what it is; declaring before use. You mean that declaring twice is smarter than declaring just once? You're actively trying to deceive me here? Nothing is declared twice as in two times, but the declaration is split in two pieces. Btw, 9 times out of 10 the type declaration is reused multiple times so in the end it saves typing. I try to make myself more clear. Of course the based construct comes useful when you're dealing with structured data such as records. And of course you need a type declaration for your record. But currently you need a second type declaration for a pointer to that record. This is not a split declaration, but an extra declaration. one for the typed pointer itself. The Pascal type is visible in the pointer type declaration, and not in the pointer declaration (which is in a different section, var vs. type, which in a large program can be That's why names were invented in programming languages. Names can add meaning to types. It can make the reader see structure instead of chaos. The record type name is meaningful, the pointer type name is not. The usual way is to use the same name of the record, prepended by a P. If it can be inferred from the structure name, it's pleonastic. If it can't it's obfuscating. The based construct makes it implicit. It would be more consistent with the rest of the language, but what I suggest is to push consistency on the opposite direction. The opposite direction is the wrong direction. I've never found the C++ way (Button-Click) more telling than FPC way (Button.Click), on the contrary I find it cumbersome, but of course you're free to think otherwise. -- Giuliano Colla Whenever people agree with me, I always feel I must be wrong (O. Wilde) ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Could FPC add the PLM based construct?
Giuliano Colla wrote: I've never found the C++ way (Button-Click) more telling than FPC way (Button.Click), on the contrary I find it cumbersome, but of course you're free to think otherwise. Huh? Button.Click is perfectly legal in C++... Although it does not mean a dereference, but a direct ;) AFAIK the scandinavian mafia (Bjarne and Anders) did not agree, but both had the same in mind. Since Pascal already used ^ for pointers (pascal is much older than c++) Anders was free to use the simple dot notation to distinguish. Bjarne had to circumvent his reliance on C notation, hence the -. I don't see the point about your argumentation. Absolute is supported, even explicit as opposed to implicit and that is a good thing. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Could FPC add the PLM based construct?
Thaddy ha scritto: Giuliano Colla wrote: I've never found the C++ way (Button-Click) more telling than FPC way (Button.Click), on the contrary I find it cumbersome, but of course you're free to think otherwise. Huh? Button.Click is perfectly legal in C++... Not if Button is a pointer. C++ makes a difference wether between Button.Click (direct) and Button-Click (dereference). FPC, in case of objects does not. -- Giuliano Colla Whenever people agree with me, I always feel I must be wrong (O. Wilde) ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Could FPC add the PLM based construct?
Giuliano Colla wrote: var Pfoo: pointer; foo: any valid FPC Type based Pfoo; or foo: based Pfoo any valid FPC type; . Pfoo: pointer; PBfoo: PByte absolute Pfoo; PIfoo: PInteger absolute Pfoo; I don't see the difference between based and absolute, except order of keywords? Micha ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Could FPC add the PLM based construct?
Micha Nelissen ha scritto: Giuliano Colla wrote: var Pfoo: pointer; foo: any valid FPC Type based Pfoo; or foo: based Pfoo any valid FPC type; . Pfoo: pointer; PBfoo: PByte absolute Pfoo; PIfoo: PInteger absolute Pfoo; I don't see the difference between based and absolute, except order of keywords? With based you declare a variable name, which you access directly, without need of an extra type declaration. Pfoo is the pointer, foo is the variable, no ambiguity. With absolute you need a) to declare an extra type (PByte, or whatever), b) to explicitly access the variable through the pointer (PBfoo^ as opposed to foo). But if the variable is an array or a string, then you have ambiguities wether Pfoo means the variable or the pointer. Order of keywords of course is not relevant, I just picked up the first one coming to my mind. -- Giuliano Colla Whenever people agree with me, I always feel I must be wrong (O. Wilde) ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Could FPC add the PLM based construct?
Giuliano Colla wrote: With absolute you need a) to declare an extra type (PByte, or Declaring an extra type is one of those things that make Pascal what it is; declaring before use. whatever), b) to explicitly access the variable through the pointer (PBfoo^ as opposed to foo). But if the variable is an array or a string, So we're talking about saving typing of a '^' ? Explicitly typing a '^' when you're derefencing a pointer makes the code more readable, not less. Micha ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Could FPC add the PLM based construct?
On Mon, 16 Nov 2009 12:17:23 +0100, Micha Nelissen wrote about Re: [fpc-devel] Could FPC add the PLM based construct?: Giuliano Colla wrote: var Pfoo: pointer; foo: any valid FPC Type based Pfoo; or foo: based Pfoo any valid FPC type; . Pfoo: pointer; PBfoo: PByte absolute Pfoo; PIfoo: PInteger absolute Pfoo; I don't see the difference between based and absolute, except order of keywords? The based keyword actually comes from PL/I, which Intel used as the basis for PL/M. The way based variables work is that they are always accessed via a pointer, but the pointer is always type-neutral. This means that the access to the addressed storage location is determined not by the pointer, but by the based variable (usually a structure). This, in turn, means that one can declare multiple structures associated with just a single pointer, each causing the compiler to generate code specific to that structure. The benefit is that there can be some indicator that tells the application *at run time* what type of structure the pointer is addressing, and the appropriate code to access the data can be executed. The synopsis is that an untyped pointer becomes like a hardware base register, which is the way pointers are meant to be. Note that PL/I also has type-associated pointers, called a handle for the associated type. These behave like Pascal pointers, in that they are rather safer, but far less flexible. -- Regards, Dave [RLU #314465] === david.w.n...@ntlworld.com (David W Noon) === ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Could FPC add the PLM based construct?
Micha Nelissen ha scritto: Giuliano Colla wrote: With absolute you need a) to declare an extra type (PByte, or Declaring an extra type is one of those things that make Pascal what it is; declaring before use. You mean that declaring twice is smarter than declaring just once? You need two declarations: one for the type of the typed pointer, and one for the typed pointer itself. The Pascal type is visible in the pointer type declaration, and not in the pointer declaration (which is in a different section, var vs. type, which in a large program can be quite far away). I hardly see the point. whatever), b) to explicitly access the variable through the pointer (PBfoo^ as opposed to foo). But if the variable is an array or a string, So we're talking about saving typing of a '^' ? Explicitly typing a '^' when you're derefencing a pointer makes the code more readable, not less. You mean that string or object references where pointers are implicitly dereferenced make the code less readable? A MyString^[3] or a MyButton^.Click would be more readable than the current MyString[3] and MyButton.Click? It would be more consistent with the rest of the language, but what I suggest is to push consistency on the opposite direction. -- Giuliano Colla Whenever people agree with me, I always feel I must be wrong (O. Wilde) ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
