в 14:21, 25 мая 2010

2010-05-25T14:21:06Z

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2010-05-25T10:27:26Z

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==A generic mode finding function.==

<source lang="cpp">
#include <iostream>
#include <cstring>
using namespace std;

template <class X> X mode(X *data, int size)
{
register int t, w;
X md, oldmd;
int count, oldcount;
oldmd = 0;
oldcount = 0;
for(t=0; t<size; t++) {
md = data[t];
count = 1;
for(w = t+1; w < size; w++)
if(md==data[w]) count++;
if(count > oldcount) {
oldmd = md;
oldcount = count;
}
}
return oldmd;
}
int main()
{
int i[] = { 1, 2, 3, 4, 2, 3, 2, 2, 1, 5};
char *p = "this is a test";
cout << "mode of i: " << mode(i, 10) << endl;
cout << "mode of p: " << mode(p, (int) strlen(p));
return 0;
}

</source>

==Creating a custom algorithm based on template==

<source lang="cpp">
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
using namespace std;
template<class ForIter>
void times2(ForIter start, ForIter end)
{
while(start != end) {
*start *= 2;
start++;
}
}
int main()
{
int i;
vector<int> vectorObject;
for(i = 0; i <10; i++)
vectorObject.push_back(i);
cout << "Initial Contents of vectorObject: ";
for(i = 0; i <vectorObject.size(); i++)
cout << vectorObject[ i ] << " ";
cout << endl;
times2(vectorObject.begin(), vectorObject.end());
cout << "Contents of vectorObject doubled: ";
for(i = 0; i <vectorObject.size(); i++)
cout << vectorObject[ i ] << " ";
cout << endl;
list<float> lst;
list<float>::iterator p;
for(i = 0; i <5; i++)
lst.push_back((float)i*3.1416);
cout << "Initial Contents of lst: ";
for(p=lst.begin(); p!=lst.end(); p++)
cout << *p << " ";
cout << endl;
times2(lst.begin(), lst.end());
cout << "Contents of lst doubled: ";
for(p=lst.begin(); p!=lst.end(); p++)
cout << *p << " ";
cout << endl;
return 0;
}

</source>

==find all template function==

<source lang="cpp">
#include <vector>
#include <iostream>
#include <functional>
#include <algorithm>
using namespace std;
template <typename InputIterator, typename Predicate>
vector<InputIterator> find_all(InputIterator first, InputIterator last, Predicate pred)
{
vector<InputIterator> res;
while (true) {
first = find_if(first, last, pred);
if (first == last) {
break;
}
res.push_back(first);
++first;
}
return (res);
}
int main(int argc, char** argv){
int arr[] = {3, 4, 5, 4, 5, 6, 5, 8};
vector<int*> all = find_all(arr, arr + 8, bind2nd(equal_to<int>(), 5));

cout << "Found " << all.size() << " matching elements: ";

for (vector<int*>::iterator it = all.begin(); it != all.end(); ++it) {
cout << **it << " ";
}
return (0);
}

</source>

==function template for getting the max value==

<source lang="cpp">
#include <iostream>
using namespace std;
template <class T>
T GetMax (T a, T b) {
return (a>b?a:b);
}
int main () {
int i=5, j=6, k;
long l=10, m=5, n;
k=GetMax(i,j);
n=GetMax(l,m);
cout << k << endl;
cout << n << endl;
return 0;
}

</source>

==Function template: swap values==

<source lang="cpp">

#include <iostream>
using namespace std;
template <class X> void swapargs(X &a, X &b)
{
X temp;
temp = a;
a = b;
b = temp;
}
int main()
{
int i=10, j=20;
float x=10.1, y=23.3;
cout << "Original i, j: " << i << " " << j << endl;
cout << "Original x, y: " << x << " " << y << endl;
swapargs(i, j); // swap integers
swapargs(x, y); // swap floats
cout << "Swapped i, j: " << i << " " << j << endl;
cout << "Swapped x, y: " << x << " " << y << endl;
return 0;
}

</source>

==Making a Sequence of Random Numbers==

<source lang="cpp">
#include <algorithm>
#include <functional>
#include <cstdlib>
#include <vector>
#include <iostream>
using namespace std;
template <class T>
void print(T& c){
for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
std::cout << *i << endl;
}
}
int main( )
{
vector<int> random( 8 );
// fill the container with random numbers
generate( random.begin(), random.end(), rand );
print( random );
}

</source>

==Overriding a template function.==

<source lang="cpp">
#include <iostream>
using namespace std;

template <class X> void swapargs(X &a, X &b)
{
X temp;

temp = a;
a = b;
b = temp;
cout << "Inside template swapargs.\n";
}

// This overrides the generic version of swapargs() for ints.
void swapargs(int &a, int &b)
{
int temp;

temp = a;
a = b;
b = temp;
cout << "Inside swapargs int specialization.\n";
}

int main()
{
int i=10, j=20;
double x=10.1, y=23.3;
char a="x", b="z";

cout << "Original i, j: " << i << " " << j << "\n";
cout << "Original x, y: " << x << " " << y << "\n";
cout << "Original a, b: " << a << " " << b << "\n";

swapargs(i, j); // calls explicitly overloaded swapargs()
swapargs(x, y); // calls generic swapargs()
swapargs(a, b); // calls generic swapargs()

cout << "Swapped i, j: " << i << " " << j << "\n";
cout << "Swapped x, y: " << x << " " << y << "\n";
cout << "Swapped a, b: " << a << " " << b << "\n";

return 0;
}

</source>

==Simple template function to accept two parameters==

<source lang="cpp">
#include <iostream>
using namespace std;
template <class type1, class type2>
void myFunction(type1 x, type2 y)
{
cout << x << " " << y << endl;
}
int main()
{
myFunction(10, "hi");
myFunction(0.23, 10L);
return 0;
}

</source>

==Template copy array function==

<source lang="cpp">
#include <iostream>
using namespace std;
template<class TYPE>
void copy(TYPE a[], TYPE b[], int n)
{
for (int i = 0; i < n; ++i)
a[i] = b[i];
}
template<class TYPE>
void print(TYPE a[], int n)
{
cout << "\nNEW PRINT =";
for (int i = 0; i < n; ++i)
cout << a[i] << " ";
}
int main()
{
double f1[50], f2[50];
char c1[25], c2[50];
int i1[75], i2[75];
int i;
for (i = 0; i < 50; ++i) { //init arrays
f1[i] = 1.1 + i;
f2[i] = 2.2 * i;
c2[i] = "A" + i/5;
}
for (i = 0; i < 25; ++i) { //init arrays
c1[i] = "a" + i/8;
}
for (i = 0; i < 75; ++i) { //init arrays
i1[i] = 2 * i;
i2[i] = i * i;
}
print(f1, 20); //print initial values
print(f2, 20);
print(i1, 20);
print(i2, 20);
print(c1, 20);
print(c2, 20);
copy(f1, f2, 50);
copy(c1, c2, 10);
copy(i1, i2, 40);
print(f1, 20); //print initial values
print(f2, 20);
print(i1, 20);
print(i2, 20);
print(c1, 20);
print(c2, 20);
}

</source>

==template function for bubble sort==

<source lang="cpp">
#include <iostream>
using namespace std;
template <class X> void bubble_sort(X *items, int size);
template <class X> void show_items(X *items, int size);
int main(void)
{
int iarray[7] = {7, 5, 4, 3, 9, 8, 6};
double darray[5] = {4.2, 2.5, -0.9, 1.2, 3.0};
cout << "Here is unsorted integer array: " << endl;
show_items(iarray, 7);
cout << "Here is unsorted double array: " << endl;
show_items(darray, 5);
bubble_sort(iarray, 7);
bubble_sort(darray, 5);
cout << "Here is sorted integer array: " << endl;
show_items(iarray, 7);
cout << "Here is sorted double array: " << endl;
show_items(darray, 5);
}
template <class X> void bubble_sort(X *items, int size)
{
register int i, j;
X temp;
for (i = 1; i < size; i++)
for (j = size-1; j >= i; j--)
if (items[j-1] > items[j])
{
temp = items[j-1];
items[j-1] = items[j];
items[j] = temp;
}
}
template <class X> void show_items(X *items, int size)
{
int i;
for(i=0; i < size; i++)
cout << items[i] << ", ";
cout << endl;
}

</source>

==template function for compacting the items==

<source lang="cpp">
#include <iostream>
using namespace std;
template <class X> void compact(X *items, int count, int start, int end);
template <class X> void show_items(X *items, int size);
int main(void)
{
int nums[7] = {0, 1, 2, 3, 4, 5, 6};
char str[18] = "Generic Functions";
cout << "Here is uncompacted integer array: ";
show_items(nums, 7);
cout << "Here is the uncompacted char array: ";
show_items(str, 18);
compact(nums, 7, 2, 4);
compact(str, 18, 6, 10);
cout << "Here is compacted integer array: ";
show_items(nums, 7);
cout << "Here is the compacted char array: ";
show_items(str, 18);
}
template <class X> void compact(X *items, int count, int start, int end)
{
register int i;
for(i=end+i; i < count; i++, start++)
items[start] = items[i];
for( ; start<count; start++)
items[start] = (X) 0;
}
template <class X> void show_items(X *items, int size){
int i;
for(i=0; i < size; i++)
cout << items[i];
cout << endl;
}

</source>

==template function for find a value==

<source lang="cpp">
#include <iostream>
#include <cstring>
using namespace std;
template <class X> int find(X object, X *list, int size)
{
int i;
for(i = 0; i <size; i++)
if(object == list[ i ])
return i;
return -1;
}
int main()
{
int a[] = {1, 2, 3, 4};
char *c = "this is a test";
double d[] = {1.1, 2.2, 3.3};
cout << find(3, a, 4);
cout << endl;
cout << find("a", c, (int) strlen(c));
cout << endl;
cout << find(0.0, d, 3);
return 0;
}

</source>

==Use a Function Object to Hold state==

<source lang="cpp">
#include <algorithm>
#include <iostream>
#include <vector>
#include <list>
using namespace std;
template <typename elementType>
struct DisplayCounter
{
int m_nCount;
DisplayCounter ()
{
m_nCount = 0;
}
// Display the element, hold count!
void operator () (const elementType& element)
{
++ m_nCount;
cout << element << " ";
}
};
int main ()
{
vector <int> v;
for (int nCount = 0; nCount < 10; ++ nCount)
v.push_back (nCount);
DisplayCounter <int> mResult;
mResult = for_each ( v.begin (), v.end (), DisplayCounter <int> () );
cout << """ << mResult.m_nCount << "" elements were displayed!" << endl;
return 0;
}

</source>

==Using a Binary Function to Multiply Two Ranges==

<source lang="cpp">
#include <vector>
#include <iostream>
#include <algorithm>
template <typename elementType>
class CMultiply
{
public:
elementType operator () (const elementType& elem1,const elementType& elem2){
return (elem1 * elem2);
}
};
int main (){
using namespace std;
vector <int> v1, v2, vecResult;
for (int nCount1 = 0; nCount1 < 10; ++ nCount1)
v1.push_back (nCount1);
for (int nCount2 = 100; nCount2 < 110; ++ nCount2)
v2.push_back (nCount2);
vecResult.resize (10);
transform ( v1.begin(),
v1.end(),
v2.begin(), // multiplier values
vecResult.begin(), // range that holds result
CMultiply <int>() ); // the function that multiplies
for (size_t nIndex1 = 0; nIndex1 < v1.size (); ++ nIndex1)
cout << v1 [nIndex1] << " ";
for (size_t nIndex2 = 0; nIndex2 < v2.size (); ++nIndex2)
cout << v2 [nIndex2] << " ";
for (size_t nIndex = 0; nIndex < vecResult.size (); ++ nIndex)
cout << vecResult [nIndex] << " ";
return 0;
}

</source>

==Using Standard Parameters with Template Functions==

<source lang="cpp">
#include <iostream>
using namespace std;

const int TABWIDTH = 8;

// Display data at specified tab position.
template<class X> void tabOut(X data, int tab)
{
for(; tab; tab--)
for(int i=0; i<TABWIDTH; i++) cout << " ";

cout << data << "\n";
}

int main()
{
tabOut("This is a test", 0);
tabOut(100, 1);
tabOut("X", 2);
tabOut(10/3, 3);

return 0;
}

</source>

==write function object==

<source lang="cpp">
#include <functional>
#include <algorithm>
#include <cctype>
#include <string>
#include <iostream>
using namespace std;
class myIsDigit : public unary_function<char, bool>{
public:
bool operator() (char c) const { return (::isdigit(c)); }
};
bool isNumber(const string& str){
string::const_iterator it = find_if(str.begin(), str.end(),not1(myIsDigit()));
return (it == str.end());
}
int main(int argc, char** argv){
cout << isNumber("12345") << endl;
cout << isNumber("hello") << endl;
cout << isNumber("1234a") << endl;
return (0);
}

</source>

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