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Talk:Generator/Exponential: Difference between revisions
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::: Also, I think "Sequence generator" could be misleading, given that sequences can als be data structures which can be generated without a requirement for mutating state. --[[User:Rdm|Rdm]] 15:01, 8 June 2011 (UTC)
:::: How about "Mutating state generator"? [[User:Markhobley|Markhobley]] 07:52, 13 July 2011 (UTC)
== C++ code ==
The C++ code should probably be an implementation of forward_iterator. I'd do it myself, but I don't know how (working on that is what led me back to this page) --[[User:Short Circuit|Michael Mol]] 14:08, 1 July 2011 (UTC)
:What, like this? <lang Cpp>#include <iostream>
#include <iterator>
template<int p>
class PowerSeq : public std::iterator<std::forward_iterator_tag, int> {
public:
PowerSeq(int first = 0 ) { pos = first; }
int operator *() { return calc(); }
PowerSeq<p>& operator ++() {
pos ++;
return *this;
}
PowerSeq<p> operator ++(int) {
PowerSeq<p> tmp(pos);
pos ++;
return tmp;
}
protected:
int pos;
int calc() {
int out = pos;
for (int i = 1; i < p; i++) out *= pos;
return out;
}
};
template<int in, int without>
class PowerSeqFilter : public std::iterator<std::forward_iterator_tag, int> {
public:
PowerSeqFilter(int p1 = 0, int p2 = 0) { // NB. should check in != without
s1 = PowerSeq<in>(p1);
s2 = PowerSeq<without>(p2);
if (*s1 == *s2) ++*this;
};
int operator *() { if (*s1 == *s2) ++*this; return *s1; }
PowerSeqFilter<in, without>& operator ++() {
do {
++s1;
while (*s1 > *s2) ++s2;
} while (*s1 == *s2);
return *this;
}
PowerSeqFilter<in, without> operator ++(int) {
PowerSeqFilter<in, without> tmp(*s1, *s2);
++*this;
return tmp;
}
protected:
PowerSeq<in> s1;
PowerSeq<without> s2;
};
int main()
{
PowerSeqFilter<2, 3> f;
for (int i = 0; i < 30; ++i, f++) {
if (i >= 20)
std::cout << i << " " << *f << std::endl;
}
}</lang>
:Personally I find this unnecessarily complicated for the task. --[[User:Ledrug|Ledrug]] 01:58, 2 July 2011 (UTC)
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