Digression: Code and Data Structure Should be in Harmony

Michael A. Jackson wrote a really brilliant book about this
Principles of Program Design (1975)
His idea:
- The control stucture of the program should mirror the structure of the input the program gets
- The control stucture of the program should mirror the structure of the output the program produces
- You get a tricky problem when input and output have different structures
- You need to harmonize the two structures with your program