Scheme programming examples

Animations

• example1.scm, which displays a blue disk.
• example2.scm, which displays a blue disk that gets larger each second.
• example3.scm, which displays the word "hello" in green, 18-point font, and adds on the letter "d" at the end each second.
• example4.scm, which displays a digital counter (in green, 18-point font) which increases by one each half second.
• example5.scm, which is just like example 2 except that it stops when the disk reaches a diameter of 40.
• example6.scm, which displays a blue disk that moves right or left when you press the right or left arrow on the keyboard.
• example7.scm, which displays a blue disk that moves right, left, up, or down when you press the corresponding arrow on the keyboard. Note that this requires using a posn as the world, rather than something simple like a number or a string.
• switch-color.scm, which displays a disk that switches colors between red and green every second, representing the state of the world with a boolean (true for red, false for green).
• switch-color-2.scm, which behaves the exact same way but represents the state of the world with a string ("red" or "green").

April 21: local and auxiliary functions

• largest_v1.scm, which computes the largest of a list of numbers. It takes an incredibly long time to find the largest of an increasing list.
• largest_v2.scm, which does the same thing much faster by using a local variable.
• largest_v3.scm, which uses an auxiliary "bigger" function instead.
• largest_v4.scm, which puts the auxiliary "bigger" function inside a local definition. Unfortunately, this redefines the "bigger" function once for each element of the list, which seems inefficient. So...
• largest_v5.scm, which defines "bigger" locally once, along with a recursive "helper" function, and the main "largest" function simply calls "helper" in the presence of "bigger".
• sort_v1.scm, which sorts a list of numbers in increasing order.
• sort_v2.scm, which does the same thing with the auxiliary function defined locally.
• sort_v3.scm, which defines both the auxiliary function and a recursive "helper" function locally, so the auxiliary function is only defined once.