1	CS 211: Introduction to Computer Programming II Instructor: Brian M. Dennis Teaching Assistants: Tom Lechner, Bin Lin http://www.cs.northwestern.edu/~bmd/cs211/
2	Logical Operators int fib(int n) { if (n < 0) return 0; if (n == 0) return 0; if (n == 1) return 1; return fib(n-1) + fib(n-2); }
3	Logical Operators int fib(int n) { if ((n < 0) \|\| (n == 0)) return 0; if (n == 1) return 1; return fib(n-1) + fib(n-2); }
4	Logical Operators // (0 <= x) && (x < 100) #include <cmath> double safe_invert(double val) { double z = 0.0; bool foo = false; foo = ((0.0 != val) && (z = 1.0 / val)); return z; }
5	Unary Operators // ! is the unary logical negation operator !((0 <= x) && (x <= 100)) è (!(0 <= x)) \|\| (!(x <= 100)) è (x < 0) \|\| (x > 100)
6	If statement int fib(int n) { if (n < 0) return 0; if (n == 0) return 0; if (n == 1) return 1; return fib(n-1) + fib(n-2); }
7	If/else statement int fib(int n) { if ((n < 0) \|\| (n == 0)) return 0; if (n == 1) return 1; else n = n – 1; return fib(n-1) + fib(n-2); }
8	If/elseif/else statement int fib(int n) { if (n < 0) { return 0; } else if (n == 0) { return 0; } else if (n == 1) { return 1; } else { n = n – 1; return fib(n-1) + fib(n-2); } }
9	switch statement int fib(int n) { int res = 0; switch(n) { case "blah": res = 0; case 1.0: res = 1; break; case res: default: res = fib(n-1) + fib(n-2); } return res; }
10	do/while statement int fib_iter_helper(int a, int b, int count); int fib_iter(int n) { return fib_iter_helper(1, 0, n); } int fib_iter_helper(int a, int b, int count) { if (count == 0) return b; return fib_iter_helper(a + b, a, count - 1); }
11	do/while statement int fib_pure_iter(int n) { int a = 1; int b = 0; int old_a; do { old_a = a; a = a + b; b = old_a; n = n - 1; } while (0 < n); return b; }
12	while statement int fib_pure_iter(int n) { int a = 1; int b = 0; int old_a = 1; while (0 < n) { old_a = a; a = a + b; b = old_a; n = n - 1; } return b; }
13	for statement int fib_pure_iter(int n) { int a = 1; int b = 0; int old_a = 1; for (int i = 0; i < n; i = i + 1) { old_a = a; a = a + b; b = old_a; } return b; }
14	for statement int fib_pure_iter(int n) { int a, b, old_a; for (a = 1, b = 0, old_a = 1; 0 < n; n = n - 1 ) { old_a = a; a = a + b; b = old_a; }; return b; }
15	Parameter passing void swap(int x, int y) { int old_x = x; x = y; y = old_x; } int main() { int x = 10, y = 20; swap(x, y); cout << "x: " << x; cout << " y: " << y; cout << "\n"; return 1; }
16	Parameter passing void swap(int& x, int &y) { int old_x = x; x = y; y = old_x; } int main() { int foo = 10, bar = 20; swap(x, y); cout << "x: " << x; cout << " y: " << y; cout << "\n"; return 1; }
17	That’s a Wrap Takeaways Logical operators Conditional/selection Iteration constructs Call by reference Reading 2.1 – 2.7, 2.13 – 2.20 Get HW2 turnin instructions