C++/STL Algorithms Modifying sequence operations/replace if
Replace value equal to 70 with 42 in a deque
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <set>
#include <deque>
#include <algorithm>
using namespace std;
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
int main()
{
set<int,greater<int> > coll1;
deque<int> coll2;
// insert elements from 1 to 9
for (int i=1; i<=9; ++i) {
coll1.insert(i);
}
PRINT_ELEMENTS(coll1,"initialized: ");
// transform all elements into coll2 by multiplying 10
transform (coll1.begin(),coll1.end(), // source
back_inserter(coll2), // destination
bind2nd(multiplies<int>(),10)); // operation
PRINT_ELEMENTS(coll2,"transformed: ");
// replace value equal to 70 with 42
replace_if (coll2.begin(),coll2.end(), // range
bind2nd(equal_to<int>(),70), // replace criterion
42); // new value
PRINT_ELEMENTS(coll2,"replaced: ");
}
/*
initialized: 9 8 7 6 5 4 3 2 1
transformed: 90 80 70 60 50 40 30 20 10
replaced: 90 80 42 60 50 40 30 20 10
*/
std::replace_if with predicate
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
bool greater9( int );
int main()
{
int a[ 10 ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 };
std::ostream_iterator< int > output( cout, " " );
std::vector< int > v3( a, a + 10 ); // copy of a
cout << "Vector v3 before replacing values greater than 9:\n ";
std::copy( v3.begin(), v3.end(), output );
// replace values greater than 9 in v3 with 100
std::replace_if( v3.begin(), v3.end(), greater9, 100 );
cout << "\nVector v3 after replacing all values greater"
<< "\nthan 9 with 100s:\n ";
std::copy( v3.begin(), v3.end(), output );
cout << endl;
return 0;
}
bool greater9( int x )
{
return x > 9;
}
/*
Vector v3 before replacing values greater than 9:
10 2 10 4 16 6 14 8 12 10
Vector v3 after replacing all values greater
than 9 with 100s:
100 2 100 4 100 6 100 8 100 100
*/
Truncate numbers to fall between 0 and 255 inclusive
#include <algorithm>
#include <functional>
#include <iomanip>
#include <numeric>
#include <string>
#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;
}
}
bool in_string( char c, const string target ){
return target.find( c ) != string::npos;
}
int main( ){
vector<float> v( 5, 1 );
partial_sum( v.begin(), v.end(), v.begin() );
print( v);
transform( v.begin(), v.end(), v.begin(),bind1st( multiplies<float>(), 100 ) );
v.assign( v.size(), 100 );
v[0] = -10;
replace_if( v.begin(), v.end(),bind2nd( greater<float>(), 255 ), 255 );
replace_if( v.begin(), v.end(), bind2nd( less<float>(), 0 ), 0 );
print( v);
}