6.4 Reasons for defining functions

Improving program readability

NOT EASY TO UNDERSTAND

EASY TO UNDERSTAND

Modular Program Development

• Modular development is the process of dividing a program into separate modules that can be developed and tested separately and then integrated into a single program.
  • A programmer can use function stubs (described in depth elsewhere) to capture the high-level behavior of the required functions (or modules) before diving into details of each function, like planning a route for a road trip before starting to drive.

Avoid writing redundant code

• A function can be defined once, then called from multiple places in a program, thus avoiding redundant code
  • Examples of such functions are math module functions like sqrt() that make it to where square root doesn't need to be programmed each time
• The skill of decomposing a program's behavior into a good set of functions is a fundamental part of programming that helps characterize a good programmer.
• Each function should have easily-recognizable behavior, and the behavior of the main program should be easily understandable via the sequence of function calls.
• A general guideline (especially for beginner programmers) is that a function's definition usually shouldn't have more than about 30 lines of code, although this guideline is not a strict rule.