Gray code
Karnaugh maps
Create functions to encode a number to and decode a number from Gray code.

Display the normal binary representations, Gray code representations, and decoded Gray code values for all 5-bit binary numbers (0-31 inclusive, leading 0's not necessary).

There are many possible Gray codes. The following encodes what is called "binary reflected Gray code."

Encoding (MSB is bit 0, b is binary, g is Gray code):

if b[i-1] = 1
   g[i] = not b[i]
else
   g[i] = b[i]
Or:

g = b xor (b logically right shifted 1 time)
Decoding (MSB is bit 0, b is binary, g is Gray code):

b[0] = g[0]

for other bits:
b[i] = g[i] xor b[i-1]
Reference
 Converting Between Gray and Binary Codes. It includes step-by-step animations.
import "/fmt" for Fmt
 
var toGray = Fn.new { |n| n ^ (n>>1) }
 
var fromGray = Fn.new { |g|
    var b = 0
    while (g != 0) {
        b = b ^ g
        g = g >> 1
    }
    return b
}
 
System.print("decimal  binary  gray    decoded")
for (b in 0..31) {
    System.write("  %(Fmt.d(2, b))     %(Fmt.bz(5, b))")
    var g = toGray.call(b)
    System.write("   %(Fmt.bz(5, g))")
    System.print("   %(Fmt.bz(5, fromGray.call(g)))")
}