CS 211:
Introduction to Computer Programming II

	Instructor: Brian M. Dennis
	Teaching Assistants:
	Tom Lechner, Bin Lin
	http://www.cs.northwestern.edu/~bmd/cs211/

Our Last Valid Program

	#include <iostream>
	using namespace std;
	main() {
	int integer_temp =  1 + 1;
	cout << "1 + 1 = " << integer_temp << "\n";
	float floating_point_temp;
	floating_point_temp = 1.414f;
	cout << "Root 2 = " << floating_point_temp
	<< "\n";
	}

Procedure Invocation

	#include <cmath>
	#include <iostream>
	using namespace std;
	main() {
	double two = 2.0;
	cout << "Root 2.0 is: " << sqrt(two) << "\n";
	}

Procedure Invocation

	#include <cmath>
	#include <iostream>
	using namespace std;
	main() {
	double two = 2.0;
	cout << "Root 2.0 squared is: "
	<< sqrt(two) * sqrt(two) << "\n";
	}

Procedure Definition

	#include <cmath>
	#include <iostream>
	using namespace std;
	main() {
	}
	// Coming from a Schemish perspective
	square(x) {
	x * x;
	}

Procedure Definition

	#include <cmath>
	#include <iostream>
	using namespace std;
	main() {
	}
	double square(double x) {
	return x * x;
	}

Procedure Definition

	#include <cmath>
	#include <iostream>
	using namespace std;
	main() {
	cout << "2.11 squared is: " << square(2.11)
	<< "\n";
	}
	double square(double x) {
	return x * x;
	}

Procedure Definition

	#include <cmath>
	#include <iostream>
	using namespace std;
	double square(double x);
	main() {
	cout << "2.11 squared is: " << square(2.11)
	<< "\n";
	}
	double square(double x) {
	return x * x;
	}

Procedure Definition

	#include <cmath>
	#include <iostream>
	using namespace std;
	double square(double x);
	int main() {
	double foo = 2.11;
	cout << "2.11 squared is: " << square(foo)
	<< "\n";
	}
	double square(double x) {
	return x * x;
	}

Recursive Procedures

	(define (fib n)
	(cond ((= n 0) 0)
	((= n 1) 1)
	(else
	(+ (fib (- n 2))
	(fib (- n 1))))
	))

Recursive Procedures

	#include <iostream>
	using namespace std;
	int fib(int n) {
	if (n == 0) return 0;
	if (n == 1) return 1;
	return fib(n-2) + fib(n-1);
	}
	int main() {
	// call fib
	}

Dynamically Typed Languages

Statically Typed Languages

Scoping

Scoping

Scoping

Storage & Lifetime

Last In, First Out == Stack

	C++ procedures
		strictly LIFO
		No nesting
	Automatic storage
		Is automatically reclaimed after procedure returns

That’s a Wrap

	Take aways
		Procedure invocation
		Procedure definition
		Procedure declaration
	Variables
		Scoping rules
		Storage rules