- Declare function in C++ - 13 Updates
- St. Paul, Minnesota - 8 Updates
- What is "TP_NUM_C_BUFS"? - 4 Updates
| "Tuấn Trần" <trananhtuan260493@gmail.com>: Apr 12 09:46PM -0700 Hi, I face a declaration function in C++ BUT I don't know what's this mean! This is my code: bool Check() const; Can you explain this for me? Thanks! |
| Wouter van Ooijen <wouter@voti.nl>: Apr 13 07:34AM +0200 Op 13-Apr-16 om 6:46 AM schreef Tuấn Trần: > bool Check() const; > Can you explain this for me? > Thanks! If you want to program in C++ and you don't understand what a function declaration is or means than my conclusion is that you should read an (introductory) book on C++ or even C. If you con't know what a specific part of that declaration (for instance the 'const') means you should ask a more specific question. Wouter van Ooijen |
| "Tuấn Trần" <trananhtuan260493@gmail.com>: Apr 13 01:31AM -0700 Vào 12:35:02 UTC+7 Thứ Tư, ngày 13 tháng 4 năm 2016, Wouter van Ooijen đã viết: > If you con't know what a specific part of that declaration (for instance > the 'const') means you should ask a more specific question. > Wouter van Ooijen Hi, Yes, I don't know what 'const' mean in declaration! Can you explain this for me? |
| Robert Wessel <robertwessel2@yahoo.com>: Apr 13 03:51AM -0500 On Tue, 12 Apr 2016 21:46:32 -0700 (PDT), Tu?n Tr?n >This is my code: >bool Check() const; >Can you explain this for me? Assuming that's a member function, it declares a const member function, which cannot alter any non-static or non-mutable data members in the class. It allows the (const) member function to be called on a const instance of the class (since the const member function cannot modify - with the exceptions noted above - the class). This is a C++11 feature. |
| Juha Nieminen <nospam@thanks.invalid>: Apr 13 10:20AM > called on a const instance of the class (since the const member > function cannot modify - with the exceptions noted above - the class). > This is a C++11 feature. What do you mean it's a C++11 feature? --- news://freenews.netfront.net/ - complaints: news@netfront.net --- |
| Paavo Helde <myfirstname@osa.pri.ee>: Apr 13 03:19PM +0300 On 13.04.2016 11:51, Robert Wessel wrote: > called on a const instance of the class (since the const member > function cannot modify - with the exceptions noted above - the class). > This is a C++11 feature. According to https://www.usenix.org/legacy/publications/compsystems/1989/sum_stroustrup.pdf , const member functions were defined and implemented in August 1985. |
| Paavo Helde <myfirstname@osa.pri.ee>: Apr 13 03:32PM +0300 On 13.04.2016 15:19, Paavo Helde wrote: > According to > https://www.usenix.org/legacy/publications/compsystems/1989/sum_stroustrup.pdf > , const member functions were defined and implemented in August 1985. Oops sorry, more careful reading says it was later than August 1985, sometime in 1985-1989. |
| "Öö Tiib" <ootiib@hot.ee>: Apr 13 08:57AM -0700 > members in the class. It allows the (const) member function to be > called on a const instance of the class (since the const member > function cannot modify - with the exceptions noted above - the class). What do you mean by "cannot modify the class"? |
| Daniel <danielaparker@gmail.com>: Apr 13 09:13AM -0700 > it declares a const member function, which cannot alter ... non-mutable > data members in the class. Presumably all member functions, const or otherwise, can't alter non-mutable data members, to the extent that that non-mutability can be expressed in the class member definition. More generally, the caller of a const member function has no guarantee that the call won't mutate data that can reasonably be thought of as belonging to the object, in some cases even without the use of const_cast. There are no circumstances in which const can be equated with pure, so it provides no help to the compiler and limited help to the programmer attempting to reason about his code. Daniel |
| David Brown <david.brown@hesbynett.no>: Apr 13 08:43PM +0200 On 13/04/16 18:13, Daniel wrote: > Presumably all member functions, const or otherwise, can't alter non-mutable > data members, to the extent that that non-mutability can be expressed in the > class member definition. "mutable" is a type qualifier that can apply to members of a class. It means that the member in question /can/ be modified by a "const" member function. Members that are not declared as mutable cannot be modified by a const member function (you can cheat, using const_cast or similar methods, but the results are undefined - and the compiler can optimise on the assumption that you don't cheat). > More generally, the caller of a const member function has no guarantee that > the call won't mutate data that can reasonably be thought of as belonging > to the object, in some cases even without the use of const_cast. That is correct - as long as you qualify such "private" data as "mutable". The caller of a const member function does have a guarantee that data, even if it is private to the object, will not be modified unless it is mutable. > There are no circumstances in which const can be equated with pure, so > it provides no help to the compiler and limited help to the programmer > attempting to reason about his code. const is not the same as "pure", and does not offer quite as many optimisation opportunities as one might think, but it helps programmers reason about their code and spot mistakes (by making some kinds of errors into compile-time errors, and by documenting functionality of the code), and it provides a number of optimisation chances to the compiler. |
| Daniel <danielaparker@gmail.com>: Apr 13 12:44PM -0700 On Wednesday, April 13, 2016 at 2:43:18 PM UTC-4, David Brown wrote: > "mutable" is a type qualifier that can apply to members of a class. > It means that the member in question /can/ be modified by a "const" > member function. Missed that, I was interpreting "non-mutable" in it's literal sense. > Members that are not declared as mutable cannot be modified > by a const member function [without cheating] Not entirely, e.g. class A { int* x; ... void f() const { x[0] = 1; } }; > reason about their code and spot mistakes (by making some kinds of > errors into compile-time errors, and by documenting functionality of the > code), and it provides a number of optimisation chances to the compiler. const is a hack in a language full of them, I don't think we will see it copied in more modern languages. Daniel |
| Victor Bazarov <v.bazarov@comcast.invalid>: Apr 13 03:50PM -0400 On 4/13/2016 3:44 PM, Daniel wrote: > x[0] = 1; > } > }; There is no modification of a *member* here. So, yes, *entirely*. V -- I do not respond to top-posted replies, please don't ask |
| Daniel <danielaparker@gmail.com>: Apr 13 01:01PM -0700 On Wednesday, April 13, 2016 at 3:51:14 PM UTC-4, Victor Bazarov wrote: > > } > > }; > There is no modification of a *member* here. So, yes, *entirely*. From the user's point of view, the function is mutating data that is owned by the object. Daniel |
| woodbrian77@gmail.com: Apr 12 07:59PM -0700 I'd like to start a C++ meeting in the St. Paul, Minnesota area. By the grace of G-d, I'm able to provide a meeting area in a conference room in the office building where Ebenezer Enterprises is, and I would be happy to give a talk or two. If you are interested in this, please let me know. Brian Ebenezer Enterprises - In G-d we trust. http://webEbenezer.net |
| Juha Nieminen <nospam@thanks.invalid>: Apr 13 06:08AM > conference room in the office building where Ebenezer Enterprises > is, and I would be happy to give a talk or two. If you are > interested in this, please let me know. I don't think anybody will be interested in your proselytizing. --- news://freenews.netfront.net/ - complaints: news@netfront.net --- |
| David Brown <david.brown@hesbynett.no>: Apr 13 09:26AM +0200 > conference room in the office building where Ebenezer Enterprises > is, and I would be happy to give a talk or two. If you are > interested in this, please let me know. Surely booking a conference room in your office building is standard procedure and part of the services offered by the building management - and it is provided by the grace of an email and a small booking fee, rather than requiring divine intervention? Or was your plan to make sure that only religious fanatics come to the meeting? Your religious beliefs are your own business - don't try to press them onto others. |
| woodbrian77@gmail.com: Apr 13 09:00AM -0700 On Wednesday, April 13, 2016 at 2:26:25 AM UTC-5, David Brown wrote: > procedure and part of the services offered by the building management - > and it is provided by the grace of an email and a small booking fee, > rather than requiring divine intervention? G-d gives me the strength and ability to make a living. > Or was your plan to make sure that only religious fanatics come to the > meeting? I welcome anyone that is interested. Brian Ebenezer Enterprises - "For two whole years Paul stayed there in his own rented house and welcomed all who came to see him." Acts 28:30 http://webEbenezer.net |
| Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk>: Apr 13 06:56PM +0100 > Brian > Ebenezer Enterprises - "For two whole years Paul stayed there > in his own rented house and welcomed all who came to see him." Acts 28:30 Brian, initially I thought you might have been a follower of Judaism however as you are quoting a book from the New Testament it might interest you to know, Christian, that as we know evolution is a fact we know that Jesus Christ never existed which is a good thing too because if he did exist he would be the biggest cunt in the universe. /Flibble |
| "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com>: Apr 13 09:25PM +0200 On 13.04.2016 19:56, Mr Flibble wrote: > we know evolution is a fact we > know that Jesus Christ never existed which is a good thing too because > if he did exist he would be the biggest cunt in the universe. Now now. - Alf |
| Daniel <danielaparker@gmail.com>: Apr 13 12:56PM -0700 On Wednesday, April 13, 2016 at 1:56:43 PM UTC-4, Mr Flibble wrote: A. > as we know evolution is a fact we know that Jesus Christ never existed B. > if he did exist he would be the biggest cunt in the universe. If I recall my logic classes correctly, B is true if A is true (any inference can be made from a false postulate.) The difficulty is A. Daniel |
| woodbrian77@gmail.com: Apr 13 12:56PM -0700 On Wednesday, April 13, 2016 at 12:56:43 PM UTC-5, Mr Flibble wrote: > Brian, initially I thought you might have been a follower of Judaism Hi, Leigh. I'm not the greatest apologist. I hope you will leave off with the bad words. |
| Robbie Hatley <see.my.sig@for.my.address>: Apr 12 05:23PM -0700 On 4/12/2016 1:14 PM, Paavo Helde wrote: > No, it does not (fail reliably). Try with some other compiler and you will see. > The proper wording would be "appears to fail in quite predictably way with my > compiler version and with my compiler options". The stated result (computer just says "Abort called" and ends program) depends on these exact inputs: Text: "randip.c" Pattern: "and" Replacement: "or" Change anything just slightly, and it either doesn't fail, or fails in a very different way (such as, instead of saying "abort called", says "segmentation fault, core dumped", or says "internal error: TP_NUM_C_BUFS too low: 50", or suddenly spews 500 pages of complete gibberish; I've seen this program do all of those the last few days). > Welcome to the wonderful world of C and C++ Undefined Behavior! Sort of like going on a bad drug trip. :-/ I think the reason the results of stack corruption is so unpredictable and varied is, when you over-write the stack, the results depend on exactly *what* gets clobbered. Clobber the wrong thing, and instead of saying something relatively sane like "segmentation fault", the computer suddenly spews a bunch of directory listings, or spews the contents of random C++ source files. (It did both of those, yesterday.) I suppose stack corruption could even cause worse things (over-writing disk files, damaging hardware, etc). Which is why I don't use C for complex programs. Too dangerous. I'll leave that to people more skilled than me. C++ is better in that regard, what with std::vector<int> instead of int sprat[50] = {0}; ...857 lines of code here... int LoopLimit = 87; for ( int i = 0 ; i < LoopLimit ; ++i ) { sprat[i] = SomeDamnFunc(Input[i]); } (Ooops! We just corrupted 4*37 bytes of the stack!) Yes, I've seen professional programmers at work make *exactly* that blunder, almost verbatim. C makes shooting one's self in the foot in that way easy. I convinced the guys to convert to C++ and use std::vector, std::map, std::list instead of arrays. Got rid of a lot of bugs that way. (That was back in 2001-2006 when I was actually heavily involved in doing C++ programming for a living. But I digress.) But Perl is even better in that regard. :D Even harder to screw things up. However, I'm trying to stay proficient in all 3 of those languages (while also learning Python as well), so that involves practice with things which are less "safe", such as fixed-length arrays on the stack, dynamic allocation with malloc & free, etc, in addition to the the safer approaches of C++. Which is part of why I do certain things the old-fashioned way in the C version of my Substitute() function. Playing with fire and trying not to get burned. -- Cheers, Robbie Hatley Midway City, CA, USA perl -le 'print "\154o\156e\167o\154f\100w\145ll\56c\157m"' http://www.well.com/user/lonewolf/ https://www.facebook.com/robbie.hatley |
| woodbrian77@gmail.com: Apr 12 07:35PM -0700 On Tuesday, April 12, 2016 at 7:23:24 PM UTC-5, Robbie Hatley wrote: Robbie, please don't swear here. Brian Ebenezer Enterprises - Making programming fun again. http://webEbenezer.net |
| Daniel <danielaparker@gmail.com>: Apr 12 08:04PM -0700 > On Tuesday, April 12, 2016 at 7:23:24 PM UTC-5, Robbie Hatley wrote: > Robbie, please don't swear here. Brian's right, in the context of Robbie's post, it's inappropriate to have "Damn" as part of the function name. It should be used in the name of the loop limit variable int SomeDamnLoopLimit = 87; as it's this that causes the annoyance and surprise. Best regards, Daniel |
| Rosario19 <Ros@invalid.invalid>: Apr 13 07:13AM +0200 On Mon, 11 Apr 2016 21:45:01 +0300, Paavo Helde wrote: >whenever possible. And I am still pretty sure the actual bug was in some >of those deleted 343 lines (and deleting them was a good way to get rid >of the bug!) i'm different of you while all you fear bug of your code, i like to find and correct bug of my code, and see my code to run in every places what i can not like is bug or difficult of use / understand / correct of code, i not wrote [example code library] possibly i not too much experice... "chi fa da se fa per tre" |
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