essential c++ book note 2 chapter 3

chapter 3 generic(普通，共有的) programming

1， arithmetic of pointers :

the use of template, note that find return a pointer

template <typename elemType>
elemType *find(const elemType *array, int size, const elemType &value)

in function, *(array+2) means adds 2 of the size of the elemType being addressed.

2, iterators

use generic algorithms #include<algorithm>

3, sequential containers : vector , list , dequeue

4, generic algorithms

binary_search() requires that the container be sorted

when copy one vector to another vector, we should first locate the size of new vector

vector<int> temp(vec.size());

copy(vec.begin(), vec.end(). temp.begin());

5, design a generic algorithm

one solution, replace with function call

vector<int> filter (const vector<int> &vec, int filter_value, bool (*pred)(int, int));

bool less_than(int v1, int v2){ return v1<v2 ? true : false; }

function objects

#include <functional>
sort(vec.begin(), vec.end(), greater<int>())
// great<int>() is function object

function object adapters

vector<int> filter (const vector<int> &vec, int val, less<int> <)
{
    find_if(tier, vec.end(), bind2nd(lt, val));   //bind second val to 2nd op, which means   < val
}


//also we can use template
template <typename InputIterator, typename OutputIterator,
              typename ElemType, typename Comp>
OutputIterator 
filter( InputIterator first, InputIterator last, OutputIterator at, const ElemType &val, Comp pred)
{
    find_if(first, last, bind2nd(red, val)) != last;
}

main()
{  //test
   filter(vec.begin(), vec,end(), vec2.begin(), elem_size, great<int>());
   //out put num which is > than elem_size
}

6, use map

= operator actually equals insert()

7 iterator inserters

to prevent heap leak, we should set the size of the containers beforehand

OR use inserters

unique_copy(vec.begin(), vec.end(), back_inserter(res_vec));
//since vector only have push_back() method

8, iostream iterators

it provides us another way to implement input and output

#include <iterator>

istream_iterator <string> is(cin);    //use stdin as input 
istream_iterator <string> eof;

copy(is, eof, back_inserter(vex));


ofstream out_file("1.txt");   //we can also use file as input
ostream_iterator <string> os(out_file, " ");
copy(vex.begin(), vex.end(), os);

转载于:https://www.cnblogs.com/ggppwx/archive/2011/01/07/1929870.html

essential c++ book note 2 chapter 3

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