Recursion vs. Iteration

Both recursion and iteration are important

• All modern programming languages support them
• Most compilers can compile recursive functions into efficient code
• Some problems are easy using one and difficult using the other

Use recursion when

• A recursive algorithm is obvious
• Optimal speed is not an issue
• The data being processed is recursive (e.g., a hierarchical directory structure)
• Clarity and simplicity of code is important

Use iteration when

• The problem is a natural fit for iteration (e.g., processing a 2D image)
• Efficiency is critical

Some recursive patterns are more efficient than others

• There are many recursive patterns.
• Some recursion, such as tail recursion, can be compiled into iteration.
• Other patterns, such as the doubly recursive fibonacci program, are inherently inefficient ways to do a computation.