C++ Class, Week 8 - BlitzCoder.net

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Socoder -> C/C++/C#/Other -> C++ Class, Week 8
Sun, 22 Nov 2009, 15:05
Afr0	This week in the official Socoder C++ class has been about templates. Challenges 1. Create a vector that stores a set of vectors that each store a set of integers. 2. Create a template class called Store that stores an array of T (where T is the template parameter). 3. Create an iterator, called random_iterator, that uses another iterator to iterate through a container in random order. 4. Name three places where you can get quick information about the components of the standard library (not including this book). -=-=- Afr0 Games Project Dollhouse on Github - Please fork!
Fri, 27 Nov 2009, 11:10
Phoenix	I'm not really part of the class, but seeing as no one has posted anything, I might as well answer. 1. std::vector<std::vector<int>> 2. template <typename T> struct Store { T array[10]; }; --v 3. boost::mt19937 engine((boost::uint32_t)time(0)); template <typename T> class random_iterator { public: random_iterator(T& container) : container(container) { } typename T::value_type operator() { return element; } typename T::iterator operator++() { return (element = container.begin() + boost::uniform_int<>(0, container.size()-1)(engine)); } private: typename T::iterator element; T& container; }; int main(int argc, char* argv[]) { // Generate 10 random numbers std::vector<int> vec; boost::uniform_int<> dist(1, 10); std::generate_n(std::back_insert_iterator<std::vector<int>>(vec), 10, boost::bind(dist, engine) ); // Print them 100 times with our super-duper-ultra-deluxe random iterator! random_iterator<std::vector<int>> iter(vec); for(int i = 0; i < 10; ++i) std::cout << *(++iter) << std::endl; } --v 4. www.cplusplus.com/reference/stl/ www.sgi.com/tech/stl/table_of_contents.html www.boost.org/doc/libs/1_41_0 Well, Boost isn't part of the standard library. But why does the book ask for three sites anyway? Am I the only one who finds these exercises a bit stupid? \|edit\| And as a funny little pedantic detail, question 2 is phrased erroneously. 'Template class' should be 'class template'. You'd expect a book to get it right, though... \|edit\|
Sun, 29 Nov 2009, 12:43
Afr0	1. std::vector<std::vector<int>> 2. #ifndef __STORE_H__ #define __STORE_H__ template <typename T> class Store { private: T Array[10]; }; #endif --v -=-=- Afr0 Games Project Dollhouse on Github - Please fork!
Sun, 29 Nov 2009, 15:23
Cower	I got bored, so here's a probably incorrect and overkill answer for #2: #include <stdint.h> #include <exception> template <typename T, uint32_t N=10u> class TStore { public: class invalid_index_exception : public std::exception { private: uint32_t _index; public: invalid_index_exception(uint32_t index) throw() : exception(), _index(index) { } invalid_index_exception(const invalid_index_exception& ex) throw() : exception(ex), _index(ex.index()) { } virtual ~invalid_index_exception() throw() { } invalid_index_exception& operator= (const invalid_index_exception& ex) throw() { _index = ex.index(); } virtual const char* what() const throw() { return "Invalid index for array access"; } virtual uint32_t index() const throw() { return _index; } }; private: T array[N]; public: const T& operator [](uint32_t index) const throw(invalid_index_exception&) { if ( N <= index ) throw invalid_index_exception(index); return array[index]; } T& operator [](uint32_t index) throw(invalid_index_exception&) { if ( N <= index ) throw invalid_index_exception(index); return array[index]; } const uint32_t size() const throw() { return N; } }; typedef TStore<int> Store; --v
Mon, 30 Nov 2009, 09:47
Phoenix	Maybe overkill, but nonetheless a better answer. Exception specifications are however, as far as I know, deprecated or de facto deprecated. Edited my snippet to be less stupidly abusive of STL algorithms, and to use a more conventional way of iterating.
Mon, 30 Nov 2009, 16:16
Cower	Are they deprecated? I never actually use C++ exceptions, so I just threw them in there 'cause I wanted there to be some sort of error so you don't end up writing where you shouldn't be.
Tue, 01 Dec 2009, 10:19
Phoenix	C++ Standards Committee We're still looking at deprecating exception specifications. Our current feeling is that we will deprecate them except for the ways of saying a function doesn't throw at all (e.g., the new noexcept feature, [which is] still being reviewed). Exceptions won't be deprecated, though. Only the stuff after the function parameter lists.