- Christmas Quiz 2022 - 6 Updates
- initializer_list constructor implementation - 3 Updates
- accelerate - 6 Updates
- "Why ISO C++ Is Not Enough for Heterogeneous Computing" by Intel - 3 Updates
| Roman P <invalid@example.com>: Dec 18 08:00PM 1) What happens when you divide an int variable by 0? 2) What happens when you divide a double variable by 0? 3) What happens when you overflow an int variable, that is, set it to a value beyond its range? 4) What is the difference between x = y++; and x = ++y;? 5) What is the difference between break, continue, and return when used inside a loop statement? 6) What are the three parts of a for statement and which of them are required? 7) What is the difference between the = and == operators? 8) Does the following statement compile? for ( ; ; ) ; 9) What does the underscore _ represent in a switch expression? Merry Christmas to you all. |
| Ben Bacarisse <ben.usenet@bsb.me.uk>: Dec 18 09:22PM Roman P <invalid@example.com> writes: I now see that this is cross-posted to comp.lang.c++ as well as to comp.lang.c. That's not a good idea for quizzes like this. > 1) What happens when you divide an int variable by 0? Asking what "happens" in this sort of context is a bit odd, but maybe clarifying what this might mean is part of the question? > 2) What happens when you divide a double variable by 0? > 3) What happens when you overflow an int variable, that is, set it to a > value beyond its range? And here there is even more ambiguity since a variable (what might better be called a named object) can be set in two ways, and the C standard says different things about each! > inside a loop statement? > 6) What are the three parts of a for statement and which of them are > required? The correct answer for C was made more complicated in 1999, and as for C++, well that's a whole new ball game. > 8) Does the following statement compile? > for ( ; ; ) ; > 9) What does the underscore _ represent in a switch expression? There is no switch expression in C and a switch statement can include lots of expressions. But, that aside, I'd like to see what you think the answer is. > Merry Christmas to you all. And to you too. -- Ben. |
| red floyd <no.spam.here@its.invalid>: Dec 18 01:36PM -0800 On 12/18/2022 12:00 PM, Roman P wrote: > 8) Does the following statement compile? > for ( ; ; ) ; > 9) What does the underscore _ represent in a switch expression? Do your own homework. |
| "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Dec 18 01:48PM -0800 On 12/18/2022 12:00 PM, Roman P wrote: > 1) What happens when you divide an int variable by 0? [...] Undefined behavior. |
| Siri Cruise <chine.bleu@yahoo.com>: Dec 18 02:57PM -0800 In article <tno1qh$21o4$2@dont-email.me>, > > 1) What happens when you divide an int variable by 0? > [...] > Undefined behavior. https://www.youtube.com/watch?v=JOiZP8FS5Ww Saved by zero. -- :-<> Siri Seal of Disavowal #000-001. Disavowed. Denied. Deleted. @ 'I desire mercy, not sacrifice.' /|\ Discordia: not just a religion but also a parody. This post / \ I am an Andrea Chen sockpuppet. insults Islam. Mohammed |
| "daniel...@gmail.com" <danielaparker@gmail.com>: Dec 18 03:18PM -0800 On Sunday, December 18, 2022 at 3:22:18 PM UTC-5, Roman P wrote: > 1) What happens Also of interest, what happens when you write code that calls substr on a std::basic_string<char,std::char_traits<char>,MyAllocator> when the template parameter MyAllocator is a stateful allocator? |
| Pawel Por <porparek@gmail.com>: Dec 18 02:13AM -0800 Hello, I'd like to understand the implementation of std::initializer_list constructor. I've copied the most recent std::lib implementation from git and building it with gcc 9.4.0 -std=c++2a. I get the following error: error: no matching function for call to 'custom_initializer<int>::custom_initializer(<brace-enclosed initializer list>)' I don't understand what is the basic mechanism to pass the brace-enclosed list to the constructor. Please give me some hints. Thank you in advance template<class _E> class custom_initializer { public: typedef _E value_type; typedef const _E& reference; typedef const _E& const_reference; typedef size_t size_type; typedef const _E* iterator; typedef const _E* const_iterator; private: iterator _M_array; size_type _M_len; // The compiler can call a private constructor. constexpr custom_initializer(const_iterator __a, size_type __l) : _M_array(__a), _M_len(__l) { } public: constexpr custom_initializer() noexcept : _M_array(0), _M_len(0) { } // Number of elements. constexpr size_type size() const noexcept { return _M_len; } // First element. constexpr const_iterator begin() const noexcept { return _M_array; } // One past the last element. constexpr const_iterator end() const noexcept { return begin() + size(); } }; int main(int argc, char **argv) { custom_initializer<int> ppp{1, 2, 3}; return 0; } |
| Bo Persson <bo@bo-persson.se>: Dec 18 12:33PM +0100 On 2022-12-18 at 11:13, Pawel Por wrote: > custom_initializer<int> ppp{1, 2, 3}; > return 0; > } std::initializer_list is "magic" in that the compiler knows about it and its connection to brace initializers. Your class lacks this compiler magic, so works differently (=not supported). |
| Pawel Por <porparek@gmail.com>: Dec 18 12:40PM -0800 > std::initializer_list is "magic" in that the compiler knows about it and > its connection to brace initializers. > Your class lacks this compiler magic, so works differently (=not supported). Thank you for response. Is this "magic" somehow available for the users or totally hidden. If so, how can I use it ? |
| Albert Arkwright <Albert.Arkwright@gmail.com>: Dec 18 01:25AM On 17/12/2022 20:47, Mr Flibble wrote: > We need to accelerate investment in new nuclear build and green hydrogen > technologies to counter climate change. There is a better alternative and the waste product degrades pretty quickly. It's called Nuclear Fusion: <https://youtu.be/d0OSLz9i5p8> |
| Mr Flibble <flibble@reddwarf.jmc.corp>: Dec 18 06:46AM On Sun, 18 Dec 2022 01:25:00 +0000, Albert Arkwright wrote: > There is a better alternative and the waste product degrades pretty > quickly. It's called Nuclear Fusion: > <https://youtu.be/d0OSLz9i5p8> Nuclear fusion outside of the lab is still decades away, if we ignore the Sun and thermonuclear weapons of course. :) /Flibble |
| "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Dec 17 10:56PM -0800 On 12/17/2022 12:47 PM, Mr Flibble wrote: > exists and creating more of it doesn't make the problem significantly > worse or have any bearing on solving that problem. Just my two cents. > #climatecrisis #ClimateEmergency Bob Lazar's hydrogen Corvette from years ago: https://youtu.be/Ytg23mDd1a4 We need the metal hydride to store the hydrogen. |
| scott@slp53.sl.home (Scott Lurndal): Dec 18 05:17PM >exists and creating more of it doesn't make the problem significantly >worse or have any bearing on solving that problem. Just my two cents. >#climatecrisis #ClimateEmergency Even if we were able to build enough fusion power plants (if they ever become viable) to replace the current fossil based energy supplies, (before fossil fuels run out, or there won't be enough energy to build the replacement facilities[*]) there is a hard limit on the amount that energy consumption can grow (at the current rate of growth the waste heat alone from power production and use will heat the planet surface to the boiling point of water within four centuries; with habitability eliminated in two centuries - and that's ignoring carbon dioxide emissions based warming completely). https://dothemath.ucsd.edu/2011/07/galactic-scale-energy/ [*] https://dothemath.ucsd.edu/2011/10/the-energy-trap/ Here's an open-source textbook that goes into the physics of energy production and consumption. Pretty bleak. https://escholarship.org/uc/energy_ambitions |
| scott@slp53.sl.home (Scott Lurndal): Dec 18 05:28PM >Bob Lazar's hydrogen Corvette from years ago: >https://youtu.be/Ytg23mDd1a4 >We need the metal hydride to store the hydrogen. From one of the comments on one of the lazar videos: Pretty cool stuff. Using a lithium hydride for storage is a huge improvement over pressurized/liquified hydrogen for storage and transport. The drawback is efficiency; it takes a lot more energy to separate the hydrogen from oxygen in water than you get back by burning the hydrogen. If you take the electricity used to separate the hydrogen, and store it in a lithium ion battery (for example) you can use an electric motor to run the car directly with 80-90% efficiency, and you don't need a particle accelerator to generate the hydride (particle accelerators use a lot of electricity). The hydrogen powered vehicle only captures about 30% of the electrical energy used to capture the hydrogen and manufacture the hydride as fuel energy for the vehicle. The same electricity used to generate 400 miles of hydrogen range would give you 900 miles of battery range if you used it to simply charge up a Tesla. The hydrogen-powered car does give you more energy-dense fuel storage: the hydride tanks for 400 miles of fuel weigh much less than a 400-mile range lithium-ion battery (a Model S with a 100 kWH battery pack has a 403 mile range, for example). The hydride vehicle is cool, and green, but all-electric battery-operated vehicles are more than twice as efficient, which means they cost half as much to run in kiloWatts per mile. Who killed the hydrogen car? Economics, in the form of cheap lithium ion batteries and efficient electric motors." -Steven Gulie Boeing and Airbus, realizing that their business models are at risk, given worldwide goals on reduction of CO2 emissions (a bit more than 2% of CO2 emissions are for air passenger and freight traffic) have been investigating several possible alternatives, including SAF (Sustainable Aviation Fuel, such as that made from recycled fats or from agricultural waste feedstocks), Hydrogen (Liquified or Pressurized H2 Gas either combustion or fuel cell), Electric (Battery in the 1000 to 2000km range basket) or a recent suggestion from WPI, a Magnesium Hydride slurry added to JET-A, the Mg binds to CO2 in the atmosphere and precipitates out as MgCO3 or MG(CO3)2; harmless (and actually edible) capture of the Carbon from the atmosphere making the flight carbon-negative. It does still rely on a non-renewable resource, and the energy costs of creating the MH2 slurry may be prohibitive. |
| Lynn McGuire <lynnmcguire5@gmail.com>: Dec 18 01:19PM -0600 On 12/18/2022 11:17 AM, Scott Lurndal wrote: > Here's an open-source textbook that goes into the physics of energy > production and consumption. Pretty bleak. > https://escholarship.org/uc/energy_ambitions Hot tubs for everyone ! Lynn |
| Lynn McGuire <lynnmcguire5@gmail.com>: Dec 17 07:13PM -0600 > Though I suppose it begs the question of why americans feel the need to drive > around in absurdly large utility vehicles. Insecurity perhaps or maybe posing. > But thats an argument for another newsgroup. Merika ! Lynn |
| Lynn McGuire <lynnmcguire5@gmail.com>: Dec 17 07:20PM -0600 On 12/17/2022 4:27 AM, Chris M. Thomasson wrote: >> posing. >> But thats an argument for another newsgroup. > Ever had to tow a big boat before? I tow a 5,000 lb 35 foot boom lift two or three times a year. I also manage to get myself in a foot or two of mud and water occasionally. Dadgum feral hogs. Lynn |
| scott@slp53.sl.home (Scott Lurndal): Dec 18 05:37PM >> Something that perhaps 15% of non-commercial pickup truck owners actually do. >Towing a boat up and down to Lake Tahoe from Carson City, one needs a >vehicle than can do it. That covers about 0.005% of all large pickup drivers., but doesn't answer the question posed above. That stretch of Highway 50 isn't typical, even in california or nevada (hopefully your're not taking 207). I drive that stretch of 50 annually during my labor day Yosemite- Lee Vining/Mono Lake-Tahoe journey (although every couple years, I'll take 89 or 207 from 395 just for a change of scenery). |
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