Ex 3.2: Dynamic Stack

Stack/Stack.cc

@@ -5,7 +5,8 @@
 void Stack::push(double c) {
 	if (full()) {
 		std::cout << "Stack::push() Error: stack is full" << std::endl ;
-		return ;
+
+		grow( DELTA );
 	}
 	s[count++] = c ;
 }
@@ -24,3 +25,26 @@ void Stack::inspect() {
 		std::cout << i << ": " << s[i] << std::endl;
 	}
 }
+
+void Stack::init( int in_size ) {
+	bufsize = in_size ;
+	count = 0 ;
+
+	s = new double[in_size];
+}
+void Stack::grow( int delta ) {
+	std::cout << "Growing by " << delta << std::endl;
+	double* newbuf = new double[ bufsize + delta ];
+
+	// Copy elements
+	for ( int i=0; i < count ; i++ )
+	{
+		newbuf[i] = s[i];
+	}
+
+	// Delete old Stack
+	delete[] s;
+
+	// Assign pointer
+	s = newbuf;
+}

Stack/Stack.hh

@@ -3,25 +3,32 @@
 #ifndef STACK_H
 #define STACK_H
 
-const int LEN = 80 ; // default stack length
+const int DELTA = 5 ; // default growing size
 class Stack {
 	// Interface
 	public:
-		Stack() { init(); }
-		~Stack() {}
+		Stack() { init( DELTA ); }
+		Stack( int in_size ) { init(in_size); }
+		~Stack() {
+			delete[] s;
+		}
 		int  nitems() { return count ; }
-		bool full() { return (count==LEN) ; }
+		bool full() { return (count==bufsize) ; }
 		bool empty() { return (count==0) ; }
 
 		void push( double c );
 		double pop();
 		void inspect();
 
+		void grow( int delta );
+
 	// Implementation
 	private:
-		void init() { count = 0 ; }
-		double s[LEN] ;
+		void init( int in_size );
+
+		double* s ;
 		int count ;
+		int bufsize ;
 
 };
 #endif