[Assorted-commits] SF.net SVN: assorted:[1482] sandbox/trunk/src/cc/ostream_overload.cc

[<yan...@us...>]

Revision: 1482
          http://assorted.svn.sourceforge.net/assorted/?rev=1482&view=rev
Author:   yangzhang
Date:     2009-10-13 22:53:52 +0000 (Tue, 13 Oct 2009)

Log Message:
-----------
added ostream_overload demo

Added Paths:
-----------
    sandbox/trunk/src/cc/ostream_overload.cc

Added: sandbox/trunk/src/cc/ostream_overload.cc
===================================================================
--- sandbox/trunk/src/cc/ostream_overload.cc	                        (rev 0)
+++ sandbox/trunk/src/cc/ostream_overload.cc	2009-10-13 22:53:52 UTC (rev 1482)
@@ -0,0 +1,77 @@
+// <http://www.parashift.com/c++-faq-lite/templates.html#faq-35.16>
+
+#include <iostream>
+#include <iomanip>
+
+using namespace std;
+
+// This doesn't work.
+
+#if 0
+
+template<typename T>
+class word_fmt
+{
+  public:
+    word_fmt(T x) : x_(x) {}
+    friend ostream & operator<<(ostream &o, word_fmt w);
+  private:
+    T x_;
+};
+
+template<typename T>
+ostream & operator<<(ostream &o, word_fmt<T> w) {
+  o << setfill('0') << setw(8) << hex << w.x_;
+  return o;
+}
+
+#endif
+
+// This works.
+
+#if 0
+template<typename T>
+class word_fmt
+{
+  public:
+    word_fmt(T x) : x_(x) {}
+    // Defining in-body works.
+    friend ostream & operator<<(ostream &o, word_fmt w) {
+      o << setfill('0') << setw(8) << hex << w.x_;
+      return o;
+    }
+  private:
+    T x_;
+};
+#endif
+
+// This also works: pre-declaring template, and adding `<>`.
+
+template<typename T> class word_fmt;
+template<typename T> ostream & operator<<(ostream &o, word_fmt<T> w);
+
+template<typename T>
+class word_fmt
+{
+  public:
+    word_fmt(T x) : x_(x) {}
+    // Defining in-body works.
+    friend ostream & operator<< <>(ostream &o, word_fmt w);
+  private:
+    T x_;
+};
+
+template<typename T>
+ostream & operator<<(ostream &o, word_fmt<T> w) {
+  o << setfill('0') << setw(8) << hex << w.x_;
+  return o;
+}
+
+// The rest.
+
+template<typename T> word_fmt<T> word(T x) { return word_fmt<T>(x); }
+
+int main() {
+  cout << word(3) << endl;
+  return 0;
+}


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