Talk:Generator/Exponential: Difference between revisions

Content added Content deleted

Inline

@@ Line 43: / Line 43: @@
 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)