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Chris
Guest
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 Posted: Sun Jan 29, 2006 9:00 am Post subject: syntax question |
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Hey all. Anyone who is familiar with Python programming knows that you
can have code like this:
list = [x+1 for x in range(5) ]
This code puts all the items processed by the for loop in a list plus
1. Is there a way to do this in C++? Something like:
int list[] = { x + 1 for (int x = 0; x < 5; x++); }
Or something?
Thanks for any help!
-Chris |
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Thomas Tutone
Guest
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| Posted: Sun Jan 29, 2006 12:00 pm Post subject: Re: syntax question |
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Chris wrote:
| Quote: | Hey all. Anyone who is familiar with Python programming knows that you
can have code like this:
list = [x+1 for x in range(5) ]
This code puts all the items processed by the for loop in a list plus
1. Is there a way to do this in C++? Something like:
int list[] = { x + 1 for (int x = 0; x < 5; x++); }
|
#include <vector>
int main()
{
std::vector vec;
for (int x = 0; x<5; ++x) vec.push_back(x + 1);
}
Best regards,
Tom |
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Victor Bazarov
Guest
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| Posted: Sun Jan 29, 2006 6:00 pm Post subject: Re: syntax question |
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Thomas Tutone wrote:
| Quote: | Chris wrote:
Hey all. Anyone who is familiar with Python programming knows that
you can have code like this:
list = [x+1 for x in range(5) ]
This code puts all the items processed by the for loop in a list plus
1. Is there a way to do this in C++? Something like:
int list[] = { x + 1 for (int x = 0; x < 5; x++); }
#include <vector
int main()
{
std::vector vec;
|
Did you mean
std::vector<int> vec;
or
std::vector<double> vec;
or
std::vector<long> vec;
or
what???
| Quote: | for (int x = 0; x<5; ++x) vec.push_back(x + 1);
}
|
I strongly recommend you to at least try to compile your code
before posting it. Omissions like that are easily avoidable. |
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Thomas Tutone
Guest
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| Posted: Sun Jan 29, 2006 8:00 pm Post subject: Re: syntax question |
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Victor Bazarov wrote:
| Quote: | Thomas Tutone wrote:
#include <vector
int main()
{
std::vector vec;
Did you mean
std::vector<int> vec;
or
std::vector<double> vec;
or
std::vector<long> vec;
or
what???
for (int x = 0; x<5; ++x) vec.push_back(x + 1);
}
I strongly recommend you to at least try to compile your code
before posting it. Omissions like that are easily avoidable.
|
True enough. std::vector<int> vec;
Best regards,
Tom |
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Daniel T.
Guest
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| Posted: Mon Jan 30, 2006 3:00 am Post subject: was: syntax question |
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In article <1138511019.819692.95160 (AT) g47g2000cwa (DOT) googlegroups.com>,
"Chris" <chrispatton (AT) gmail (DOT) com> wrote:
| Quote: | Hey all. Anyone who is familiar with Python programming knows that you
can have code like this:
list = [x+1 for x in range(5) ]
This code puts all the items processed by the for loop in a list plus
1.
|
In python, you could also do this by:
list = range(1, 6)
| Quote: | Is there a way to do this in C++? Something like:
int list[] = { x + 1 for (int x = 0; x < 5; x++); }
Or something?
|
What about:
vector<int> vec( dat::range(1, 6), dat::range() );
See below for how to do it...
I've made an iterator that works much like python's range function but
is more suited to c++'s algorithms.
Before I show you the class, let me show you how to use it:
int main() {
ostream_iterator<int> os( cout, ", " );
copy( range( 10 ), range(), os ); cout << "\n";
copy( range( 5, 10 ), range(), os ); cout << "\n";
copy( range( 0, 10, 3 ), range(), os ); cout << "\n";
copy( range( -10, -100, -30 ), range(), os ); cout << "\n";
}
compare the examples above to the python page describing range
<http://docs.python.org/tut/node6.html#SECTION006300000000000000000>
Maybe you have a container and you want to find out if any of the
numbers 1 to 5 are in it?
template < typename Container >
void fn( Container c ) {
typename Container::const_iterator it =
find_first_of(c.begin(), c.end(), range(1, 6), range());
if ( it != c.end() ) {
// *it == either 1, 2, 3, 4, or 5
}
}
Is that too cool or what!
---------- range.h ----------
// copywright (c) 2006 by Daniel Tartaglia
// permission to use is granted if notice is given
// email daniel_t (AT) earthlink (DOT) net with "great range" in subject the line
#include <iterator>
#include <stdexcept>
namespace dat {
class range:
public std::iterator<std::bidirectional_iterator_tag, int>
{
int value, end, step;
public:
range(): value(0), end(0), step(0) { }
explicit range(int e): value(0), end(e), step(1) { }
range(int v, int e, int s = 1): value(v), end(e), step(s)
{ if (step == 0) throw std::logic_error("range: bad step"); }
const int& operator*() const { return value; }
range& operator++() { value += step; return *this; }
range& operator--() { value -= step; return *this; }
range operator++(int)
{ range tmp(*this); value += step; return tmp; }
range operator--(int)
{ range tmp(*this); value -= step; return tmp; }
friend bool operator==(const range& lhs, const range& rhs) {
bool result = false;
if (lhs.step == 0 && (rhs.step > 0 && rhs.value >= rhs.end) ||
(rhs.step < 0 && rhs.value <= rhs.end)) result = true;
else if (rhs.step == 0 && (lhs.step > 0 && lhs.value >=
lhs.end) || (lhs.step < 0 && lhs.value <= lhs.end))
result = true;
else if (lhs.step == rhs.step && lhs.value == rhs.value &&
lhs.end == rhs.end) result = true;
return result;
}
friend bool operator<(const range& lhs, const range& rhs) {
bool result = false;
if (lhs.step != 0 && rhs.step == 0) result = true;
else if (lhs.step < 0 && lhs.value > rhs.value) result = true;
else if (lhs.step > 0 && lhs.value < rhs.value) result = true;
return result;
}
};
bool operator!=(const range& lhs, const range& rhs)
{ return !(lhs == rhs); }
}
---------- end range.h ---------- |
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Daniel T.
Guest
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| Posted: Mon Jan 30, 2006 3:00 am Post subject: Great range iterator was: syntax question |
|
|
In article <1138511019.819692.95160 (AT) g47g2000cwa (DOT) googlegroups.com>,
"Chris" <chrispatton (AT) gmail (DOT) com> wrote:
| Quote: | Hey all. Anyone who is familiar with Python programming knows that you
can have code like this:
list = [x+1 for x in range(5) ]
This code puts all the items processed by the for loop in a list plus
1.
|
In python, you could also do this by:
list = range(1, 6)
| Quote: | Is there a way to do this in C++? Something like:
int list[] = { x + 1 for (int x = 0; x < 5; x++); }
Or something?
|
What about:
vector<int> vec( dat::range(1, 6), dat::range() );
See below for how to do it...
I've made an iterator that works much like python's range function but
is more suited to c++'s algorithms.
Before I show you the class, let me show you how to use it:
int main() {
ostream_iterator<int> os( cout, ", " );
copy( range( 10 ), range(), os ); cout << "\n";
copy( range( 5, 10 ), range(), os ); cout << "\n";
copy( range( 0, 10, 3 ), range(), os ); cout << "\n";
copy( range( -10, -100, -30 ), range(), os ); cout << "\n";
}
compare the examples above to the python page describing range
<http://docs.python.org/tut/node6.html#SECTION006300000000000000000>
Maybe you have a container and you want to find out if any of the
numbers 1 to 5 are in it?
template < typename Container >
void fn( Container c ) {
typename Container::const_iterator it =
find_first_of(c.begin(), c.end(), range(1, 6), range());
if ( it != c.end() ) {
// *it == either 1, 2, 3, 4, or 5
}
}
Is that too cool or what!
---------- range.h ----------
// copywright (c) 2006 by Daniel Tartaglia
// permission to use is granted if notice is given
// email daniel_t (AT) earthlink (DOT) net with "great range" in subject the line
#include <iterator>
#include <stdexcept>
namespace dat {
class range:
public std::iterator<std::bidirectional_iterator_tag, int>
{
int value, end, step;
public:
range(): value(0), end(0), step(0) { }
explicit range(int e): value(0), end(e), step(1) { }
range(int v, int e, int s = 1): value(v), end(e), step(s)
{ if (step == 0) throw std::logic_error("range: bad step"); }
const int& operator*() const { return value; }
range& operator++() { value += step; return *this; }
range& operator--() { value -= step; return *this; }
range operator++(int)
{ range tmp(*this); value += step; return tmp; }
range operator--(int)
{ range tmp(*this); value -= step; return tmp; }
friend bool operator==(const range& lhs, const range& rhs) {
bool result = false;
if (lhs.step == 0 && (rhs.step > 0 && rhs.value >= rhs.end) ||
(rhs.step < 0 && rhs.value <= rhs.end)) result = true;
else if (rhs.step == 0 && (lhs.step > 0 && lhs.value >=
lhs.end) || (lhs.step < 0 && lhs.value <= lhs.end))
result = true;
else if (lhs.step == rhs.step && lhs.value == rhs.value &&
lhs.end == rhs.end) result = true;
return result;
}
friend bool operator<(const range& lhs, const range& rhs) {
bool result = false;
if (lhs.step != 0 && rhs.step == 0) result = true;
else if (lhs.step < 0 && lhs.value > rhs.value) result = true;
else if (lhs.step > 0 && lhs.value < rhs.value) result = true;
return result;
}
};
bool operator!=(const range& lhs, const range& rhs)
{ return !(lhs == rhs); }
}
---------- end range.h ---------- |
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