ch7 updated

7_31 to 7_35

Author: tsyw

Diff for: ch7/7_31.cc

@@ -0,0 +1,9 @@
+class Y;
+class X
+{
+	Y *pY;
+};
+class Y
+{
+	X x;
+};

Diff for: ch7/7_32.h

@@ -0,0 +1,73 @@
+#ifndef EX7_32_H
+#define EX7_32_H
+
+class Screen;
+
+class Window_mgr
+{
+public:
+	using ScreenIndex = vector<Screen>::size_type;
+	inline void clear(ScreenIndex);
+private:
+	vector<Screen> screens{Screen(24, 80, ' ')};
+};
+
+class Screen
+{
+public:
+	typedef std::string::size_type pos;
+	friend void Window_mgr::clear(ScreenIndex);
+	Screen &set(char c)
+	{
+		contents[cursor] = c;
+		return *this;
+	}
+	Screen &set(pos r, pos col, char c)
+	{
+		contents[r * width + col] = c;
+		return *this;
+	}
+	Screen &display(std::ostream &os)
+	{
+		do_display(os);
+		return *this;
+	}
+	const Screen &display(std::ostream &os) const
+	{
+		do_display(os);
+		return *this;
+	}
+	Screen() = default;
+	Screen(pos ht, pos wd, char c) : height(ht), width(wd), contents(ht * width, c) { }
+	Screen(pos ht, pos wd) : height(ht), width(wd), contents(ht * wd, ' ') { } 
+	char get() const
+	{
+		return contents[cursor];
+	}
+	char get(pos ht, pos wd) const
+	{
+		return contents[ht * width + wd];
+	} 
+	Screen &move(pos r, pos c)
+	{
+		cursor = r * width + c;
+		return *this;
+	}
+
+private:
+	void do_display(std::ostream &os) const
+	{
+		os << contents;
+	}
+	pos cursor = 0;
+	pos height = 0, width = 0;
+	std::string contents;
+};
+
+void Window_mgr::clear(ScreenIndex i)
+{
+	Screen &s = screens[i];
+	s.contents = string(s.height * s.width, ' ');
+}
+
+#endif

Diff for: ch7/7_33.cc

@@ -0,0 +1,4 @@
+// pos Screen::size() const// should be Screen::pos
+// {
+// 	return height * width;
+// }

Diff for: ch7/7_34.cc

@@ -0,0 +1 @@
+// there will be an error in dummy_fcn(pos height)

Diff for: ch7/7_35.cc

@@ -0,0 +1,15 @@
+// typedef string Type;
+// Type initVal(); // use string
+// class Exercise {
+// public:
+//     typedef double Type;
+//     Type setVal(Type); // use double
+//     Type initVal(); // use double
+// private:
+//     int val;
+// };
+
+// Type Exercise::setVal(Type parm) {  // the first is string, the second is double
+//     val = parm + initVal();     // initVal is undefined
+//     return val;
+// }