(C++) GetIncVector

 

GetIncVector is a std::vector code snippet to obtain a std::vector with incremented values, for example, with values 0,1,2,3,etc.

 

There are multiple versions of GetIncVector:

• Using C++11 std::iota
• Using C++98 custom iota
• Using a custom functor

 

 

 

 

 

Using C++11 std::iota

 

std::iota is in the C++11 STL and can be found in the header file algorithm.h.

 

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#include <algorithm> #include <iostream> #include <iterator> #include <vector> int main() {   //Create a std::vector consisting of ten zeroes   std::vector<int> v(10,0);   //Let iota assign incrementing values to the std::vector,   //starting from zero   std::iota(v.begin(),v.end(),0);   //Show the std::vector   std::copy(v.begin(),v.end(),std::ostream_iterator<int>(std::cout," ")); }

 

Screen output:

 

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0 1 2 3 4 5 6 7 8 9

 

 

 

 

 

Using C++98 custom iota

 

iota was not among the C++98 STL. Below the code shown an implementation and example of it.

 

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#include <algorithm> #include <iostream> #include <iterator> #include <numeric> #include <vector> // Numeric functions implementation -*- C++ -*- // Copyright 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 // Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library.  This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see // <http://www.gnu.org/licenses/>. /*  *  * Copyright (c) 1994  * Hewlett-Packard Company  *  * Permission to use, copy, modify, distribute and sell this software  * and its documentation for any purpose is hereby granted without fee,  * provided that the above copyright notice appear in all copies and  * that both that copyright notice and this permission notice appear  * in supporting documentation.  Hewlett-Packard Company makes no  * representations about the suitability of this software for any  * purpose.  It is provided "as is" without express or implied warranty.  *  *  * Copyright (c) 1996,1997  * Silicon Graphics Computer Systems, Inc.  *  * Permission to use, copy, modify, distribute and sell this software  * and its documentation for any purpose is hereby granted without fee,  * provided that the above copyright notice appear in all copies and  * that both that copyright notice and this permission notice appear  * in supporting documentation.  Silicon Graphics makes no  * representations about the suitability of this software for any  * purpose.  It is provided "as is" without express or implied warranty.  */ /**  *  @brief  Create a range of sequentially increasing values.  *  *  For each element in the range @p [first,last) assigns @p value and  *  increments @p value as if by @p ++value.  *  *  @param  first  Start of range.  *  @param  last  End of range.  *  @param  value  Starting value.  *  @return  Nothing.  */ template<typename _ForwardIterator, typename _Tp>   void iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value) {   // concept requirements   __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<     _ForwardIterator>)   __glibcxx_function_requires(_ConvertibleConcept<_Tp,     typename iterator_traits<_ForwardIterator>::value_type>)      __glibcxx_requires_valid_range(__first, __last);   for (; __first != __last; ++__first)   {   *__first = __value;   ++__value;   } } int main() {   std::vector<int> v(10,0);   iota(v.begin(),v.end(),0);   std::copy(v.begin(),v.end(),std::ostream_iterator<int>(std::cout," ")); }

 

Screen output:

 

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0 1 2 3 4 5 6 7 8 9

 

 

 

 

 

Using a custom functor

 

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#include <algorithm> #include <iostream> #include <iterator> #include <vector> //From http://www.richelbilderbeek.nl/CppFunctorIncrease.htm struct Increase : public std::unary_function<void,int> {   explicit Increase(const int initValue = 0) : mValue(initValue) {}   void operator()(int& anything)   {     anything = mValue;     ++mValue;   }   private:   int mValue; }; //From http://www.richelbilderbeek.nl/CppGetIncVector.htm const std::vector<int> GetIncVector(const std::size_t sz, const int init_val = 0) {   std::vector<int> v(sz,0);   std::for_each(v.begin(),v.end(),Increase(init_val));   return v; } //From http://www.richelbilderbeek.nl/CppCoutContainer.htm template <class Container> void CoutContainer(const Container& c) {   std::copy(c.begin(),c.end(),     std::ostream_iterator<typename Container::value_type>(std::cout,"\n")); } int main() {   const std::size_t sz = 5;   const std::vector<int> v = GetIncVector(sz);   CoutContainer(v); }