is anyone aware of generalized transform, for_each? - c++

er wrote:
> hi,
>
> is anyone aware of a library that generalizes transform, for_each?
> e.g.
>
> transform(
> vec1.begin(),
> vec1.end(),
> vec2.begin(),
> vec3.begin(),
> vec4.begin(),
> back_inserter(vec5),
> op
> )//where op is a 4-ary function
>

I've just written one,

template <class II, class OI, class F4>
OI transform(II first, II last, II first2, II first3, II first4, OI
dest, F4 func)
{
while (first != last)
{
*dest = func(*first, *first2, *first3, *first4);
++first;
++first2;
++first3;
++first4;
++dest;
}
return dest;
}

That will be $8000 please.

john

John Harrison wrote:
> er wrote:
>> hi,
>>
>> is anyone aware of a library that generalizes transform, for_each?
>> e.g.
>>
>> transform(
>> vec1.begin(),
>> vec1.end(),
>> vec2.begin(),
>> vec3.begin(),
>> vec4.begin(),
>> back_inserter(vec5),
>> op
>> )//where op is a 4-ary function
>>
>
> I've just written one,
>
> template <class II, class OI, class F4>
> OI transform(II first, II last, II first2, II first3, II first4, OI
> dest, F4 func)

template <typename II1, typename II2, typename II3, typename II4,
typename OI, typename F4>
OI transform(II1 first, II1 last, II2 first2, II3 first3, II4 first4,
OI dest, F4 func)

> {
> while (first != last)
> {
> *dest = func(*first, *first2, *first3, *first4);
> ++first;
> ++first2;
> ++first3;
> ++first4;
> ++dest;
> }
> return dest;
> }
>

Which allows for merging of different iterator types (list, vector,
set...) as well as different types for the values (int, float, double...)

On Sep 27, 12:13 pm, red floyd <no.s...@here.dude> wrote:
> John Harrison wrote:
> > er wrote:
> >> hi,
>
> >> is anyone aware of a library that generalizes transform, for_each?
> >> e.g.
>
> >> transform(
> >> vec1.begin(),
> >> vec1.end(),
> >> vec2.begin(),
> >> vec3.begin(),
> >> vec4.begin(),
> >> back_inserter(vec5),
> >> op
> >> )//where op is a 4-ary function
>
> > I've just written one,
>
> > template <class II, class OI, class F4>
> > OI transform(II first, II last, II first2, II first3, II first4, OI
> > dest, F4 func)
>
> template <typename II1, typename II2, typename II3, typename II4,
> typename OI, typename F4>
> OI transform(II1 first, II1 last, II2 first2, II3 first3, II4 first4,
> OI dest, F4 func)
>
> > {
> > while (first != last)
> > {
> > *dest = func(*first, *first2, *first3, *first4);
> > ++first;
> > ++first2;
> > ++first3;
> > ++first4;
> > ++dest;
> > }
> > return dest;
> > }
>
> Which allows for merging of different iterator types (list, vector,
> set...) as well as different types for the values (int, float, double...)

yes, thank you both, but this is generalized in type, not in
dimension. i should have made that clear in the first post, and
replace 4 by an arbitrary N. i'm aware that this is no trivial
task...hence my posting here.

"er" <erwann.rogard@gmail.com> wrote in message
news:1190859195.633687.264720@n39g2000hsh.googlegroups.com...
> hi,
>
> is anyone aware of a library that generalizes transform, for_each?
> e.g.
>
> transform(
> vec1.begin(),
> vec1.end(),
> vec2.begin(),
> vec3.begin(),
> vec4.begin(),
> back_inserter(vec5),
> op
> )//where op is a 4-ary function
>

See http://www.boost.org/libs/iterator/d..._iterator.html. Quote:

std::vector<double>::const_iterator beg1 = vect_of_doubles.begin();
std::vector<double>::const_iterator end1 = vect_of_doubles.end();
std::vector<int>::const_iterator beg2 = vect_of_ints.begin();
std::vector<int>::const_iterator end2 = vect_of_ints.end();

std::for_each(beg1, end1, func_0());
std::for_each(beg2, end2, func_1());
These two iterations can now be replaced with a single one as follows:

std::for_each(
boost::make_zip_iterator(
boost::make_tuple(beg1, beg2)
),
boost::make_zip_iterator(
boost::make_tuple(end1, end2)
),
zip_func()
);
struct zip_func :
public std::unary_function<const boost::tuple<const double&, const int&>&,
void>
{
void operator()(const boost::tuple<const double&, const int&>& t) const
{
m_f0(t.get<0>());
m_f1(t.get<1>());
}

private:
func_0 m_f0;
func_1 m_f1;
};
Jeff Flinn

On Sep 27, 7:59 pm, "Jeff F" <norepl...@please.com> wrote:
> "er" <erwann.rog...@gmail.com> wrote in message
>
> news:1190859195.633687.264720@n39g2000hsh.googlegroups.com...
>
> > hi,
>
> > is anyone aware of a library that generalizes transform, for_each?
> > e.g.
>
> > transform(
> > vec1.begin(),
> > vec1.end(),
> > vec2.begin(),
> > vec3.begin(),
> > vec4.begin(),
> > back_inserter(vec5),
> > op
> > )//where op is a 4-ary function
>
> Seehttp://www.boost.org/libs/iterator/doc/zip_iterator.html. Quote:
>
> std::vector<double>::const_iterator beg1 = vect_of_doubles.begin();
> std::vector<double>::const_iterator end1 = vect_of_doubles.end();
> std::vector<int>::const_iterator beg2 = vect_of_ints.begin();
> std::vector<int>::const_iterator end2 = vect_of_ints.end();
>
> std::for_each(beg1, end1, func_0());
> std::for_each(beg2, end2, func_1());
> These two iterations can now be replaced with a single one as follows:
>
> std::for_each(
> boost::make_zip_iterator(
> boost::make_tuple(beg1, beg2)
> ),
> boost::make_zip_iterator(
> boost::make_tuple(end1, end2)
> ),
> zip_func()
> );
> struct zip_func :
> public std::unary_function<const boost::tuple<const double&, const int&>&,
> void>
> {
> void operator()(const boost::tuple<const double&, const int&>& t) const
> {
> m_f0(t.get<0>());
> m_f1(t.get<1>());
> }
>
> private:
> func_0 m_f0;
> func_1 m_f1;};
>
> Jeff Flinn

thanks!