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I joined Apple in 1987, about the time they started ditching Pascal in favor of C. C++ (in the form of CFront) was just starting to be a thing. Apple's Pascal
by kabdib 9y ago
I joined Apple in 1987, about the time they started ditching Pascal in favor of C. C++ (in the form of CFront) was just starting to be a thing.
Apple's Pascal had been extended to the point where there were few true differences between it and C, other than
- strings with busted semantics (size being part of the type being a huge mistake, leading to a proliferation of types like Str255, Str32, Str31, Str64, etc). I should add that C's strings were semantically busted, too, and in more dangerous ways. No way to win :-)
- nested procedures (not terribly useful in practice, IMHO)
- an object syntax, used for Object Pascal and MacApp (a complete, though large and somewhat slow app framework).
- some miscellany, like enums and modules
Apple extended Pascal pretty extensively, adding pointer arithmetic, address-of, variant functions calls, and a bunch of things I've forgotten. I could write some Pascal, then write some C, and squint and they'd look pretty much the same. Most people shrugged and wrote new code C if they were able, and then moved to C++ when CFront became usable.
- WalterBright 9y agoI liked nested functions in Pascal, and put them in D. They turn out to be surprisingly useful: 1. Properly encapsulating their scope, as opposed to having static functions sit awkwardly somewhere else. 2. Factoring out common code within the function. 3. A lot of my need for goto statements vanished with nested functions. 4. Take the address of a nested function, and it serves as a lambda. 5. No need to create "Context" structs to pass local data to them. 6. They replace a lot of what C macros did. 7. They're inlineable, so are not costly. I use them more and more as time goes by. It's a pity C doesn't have them, they'd fit nicely into the language.
- kkylin 9y agoOff-topic, but nested functions are one of my favorite gcc extensions.
- WalterBright 9y agoI discovered with C and C++ compilers, if an extension was added that was not in the Standard, nobody would use it - not even the people who requested the extension. It wasn't like the Pascal community, where nobody would use the compiler unless it had a boatload of extensions :-)
- pjmlp 9y agoThey tried to fix that with ISO Extended Pascal, but by then compatibility with Turbo Pascal extensions was more relevant.
- kkylin 9y agoI think you're onto something (about C extensions). There was a time, before clang became default on osx, when Apple deprecated nested functions (and perhaps others) in their version of gcc, and afaik no one complained. So I may well be one of the very few. Oh well.
- anthay 9y agoIn the past I've sometimes used standard C++ local structs to nest functions. E.g.: int f() { struct local { static int nested_func() { return 123; } }; return local::nested_func(); }
- WalterBright 9y agoI've done that, too. It's clumsy and only does half the job (doesn't provide access to locals). At some point one just gets tired of the workarounds :-)
- anthay 9y agoIt's probably a bit late for this reply, but... Another clumsy workaround is to use operator(). Again, standard C++ and this one has access to local variables: int g() { int x, y; struct local { int & a_; int & b_; local(int & a, int & b) : a_(a), b_(b) {} int operator()() { return a_ + b_; } } nested(x, y); x = 99; y = 1; return nested(); } assert(g() == 100);
- nurettin 9y agoNested functions are good if you have no alternative. If you use them as lambdas or a means of code folding, (both of which don't exist in older IDEs and compilers) you will have to keep jumping around in code in order to follow the logic. That is a very tiring thing to do, especially if you just switched jobs.
- WalterBright 9y agoThere are always alternatives. The issue is how naughty or nice they are.
- kabdib 9y agoGood points, all. I think I misliked Pascal's nested procedures because they weren't true lambdas; once the outer procedure returned, the inner procs were no longer callable (just one contiguous stack, right?). Early-on, using C++ lambdas, I found myself making the same mistake in a design for some asynchronous completion stuff. Embarrassing; C++ and Pascal are not JavaScript/Lisp/Scheme/Smalltalk :-)
- asveikau 9y agoYou can assign a c++ lambda into an object for later use, you just have to be careful about capture by reference and capturing pointer types... But the capture using the copy constructor is handy here, eg. you can copy a shared_ptr and get reference counted captures... It's funny in this way how c++ lambdas lead to very c++ specific issues and uniquely c++-ish solutions. I think the wackiness of the closure capture mechanism is the best example of this I can think of.
- sidegrid 9y agoMisliked?
- frik 9y ago> nested functions in Pascal and D Or just have first class functions, and prototype based inheritance. Way more flexible and powerful than class based inheritance. See JavaScript 5 as an example, ask Crockford.
- bbrik 9y agoC# has just implemented nested functions.
- kwhitefoot 9y agoThere is a nice blog post that concisely explains why local functions are better than lambdas: https://asizikov.github.io/2016/04/15/thoughts-on-local-functions/ https://asizikov.github.io/2016/04/15/thoughts-on-local-func...
- WalterBright 9y agoC#: "Local functions can not be static." Static nested (i.e. local) functions in D can be static. What that does is prevent the function for accessing locals in the enclosing scope(s).
- vram22 9y ago>3. A lot of my need for goto statements vanished with nested functions. How does that work? Not immediately obvious to me.
- WalterBright 9y agoA lot of the goto's were used to use a common sequence of code followed by a return. With nested functions, the nested function contains the common sequence of code, and you just: T common() { ...common sequence of code... } ... return common(); instead of: goto Lcommon; ... Lcommon: ... common sequence of code ... return result;
- vram22 9y agoGot it now, thanks. But, this (the "return common();") could be done even if the function "common" was not nested within the current function, but defined outside of it, right? So what is the benefit of defining "common" as a nested function? Is it because it then has access to, and can use, variables defined in the outer function?
- WalterBright 9y agoYes, you can do it that way. But then you'll need a "context pointer" to pass references to the locals it'll need, and the function will need to be located "someplace else", meaning it is not encapsulated. I've done that for years with C and C++. Nested functions are so much nicer and clearer.
- vram22 9y agoGot it now, thanks. I've used nested functions in Python and they have some good uses. Will check them out in D.
- yuhong 9y agohttps://blogs.technet.microsoft.com/srd/2017/07/20/englishmansdentist-exploit-analysis/ https://blogs.technet.microsoft.com/srd/2017/07/20/englishma... I found out that GetString converts a Pascal string to C without a length argument!
- loeg 9y agoSpeaking of few differences from C and busted string semantics: my least favorite thing about Pascal is that strings and some types are 1-indexed, but dynamic arrays are 0-indexed. https://stackoverflow.com/questions/4083356/array-begin-from-0-or-1-in-delphi-5-0-pascal https://stackoverflow.com/questions/4083356/array-begin-from...
- yardshop 9y agoAnd the string length is in the 0 byte, meaning no strings longer than 255 bytes. At least in old Turbo Pascal anyway!
- clouddrover 9y agoYes, this is not a limitation in Free Pascal or Delphi. The ShortString type still exists and is limited to 255 bytes. But the AnsiString, WideString, and UnicodeString types are variable length and can be up to 2 gigabytes: http://docwiki.embarcadero.com/RADStudio/Berlin/en/String_Types_(Delphi) http://docwiki.embarcadero.com/RADStudio/Berlin/en/String_Ty...
- yuhong 9y agoIn the case of classic Mac OS it was part of the API.
- pjmlp 9y agoWith 640 KB it wasn't as there was a lot of space to have bigger strings. Besides, there were arrays as well, and TPW had safer strings without that limitation PCharStr.
- kabdib 9y agoOh lordy, I'd forgotten the array index thing. That was painful.
- clouddrover 9y agoThe Low and High compiler intrinsics make array indexes easy to deal with. You don't need to care about the indexing to iterate over the array. You just go from Low(array) to High(array): http://docwiki.embarcadero.com/Libraries/Berlin/en/System.Low http://docwiki.embarcadero.com/Libraries/Berlin/en/System.Lo...
- deleted 9y ago[deleted]
- gaius 9y agostrings with busted semantics (size being part of the type being a huge mistake, leading to a proliferation of types like Str255, Str32, Str31, Str64, etc). I should add that C's strings were semantically busted, too, and in more dangerous ways. No way to win :-) I think trading some programmer inconvenience for a world with no buffer overruns would have been a good thing, in retrospect!
- SingletonIface 9y agoI hadn't heard of CFront. https://en.wikipedia.org/wiki/Cfront https://en.wikipedia.org/wiki/Cfront Interesting.