Designing for Reuse

The syntax for writing Scheme programs was discussed in the Scheme tutorial in chapter 2. We must certainly understand the syntax of a programming language, but there is more to writing programs than writing a sequence of instructions to solve a problem. It is expensive to write software, so it important to write programs so that portions of the program can be reused in future programs. It is also important to document properly what the program is supposed to do (analysis of problem) and the design decisions that were used to implement the program. These topics will be introduced in chapter 4. We will discuss modularity and cohesion in this chapter. Modularity refers to separating functions into separate program modules. These fairly independent modules can more easily be reused in future programs that we write. Cohesion refers to placing in a code module (or library) functions that have similar functionality and that tend to operate on the same type of data.