DAY11
Wednesday, 06 June 2012

Today we will:

• look at how a pair of for loops can be nested (also called "double for loops"), and why you might want to do that;
• introduce the while and do loops, which repeat some statements until a condition is met;
• look at the break and continue statements for changing the way a loop is carried out (the book warns you not to use these. I disagree!);

Programs we might discuss:

• bran.c, a function which returns a random boolean value, either true or false; you don't need to understand this function. We just need to be able to use it.
• factors.c, a program which uses nested for loops to compute and display the factors of each number from 2 to n.
• fxy_min.c, a program which uses nested for loops to seek the minimum of f(x,y) in the rectangle a <= x <= b, c <= y <= d; this program uses if statements, which we officially don't know about yet.
• fxy_table.c, a program which uses nested for loops to print a table of f(x,y) in the rectangle a <= x <= b, c <= y <= d;
• matrix_multiply.c, a program which uses double for loops to multiply a matrix times a vector. This program involves arrays, which we officially don't know about yet.
• midpoint.c, a program which evaluates a function at the midpoints of n equally spaced intervals.
• midpoint.txt, the output from a run of midpoint using 10 intervals.
• midpoint.png, a plot of the midpoint data. The gnuplot command is basically

  plot "midpoint.txt" with boxes

• p5.7.c, a program from the book (example 5.7) which uses a while loop to compute the greatest common divisor of two integers.
• scientific.c, a program which uses while loops to rewrite a large or small real number in scientific notation.
• square_root.c, a program which uses a while loop to find an estimate for the square root of a number.
• vegas.c, a program which lets you specify how much money you start with, and then lets you bet repeatedly on a flip of a coin. The program illustrates the while and do/while statements as it checks that you still have money to play with, and that you didn't bet more than you have. This program needs to be run with bran.