Combine Duplication

We need to look out for three kinds of duplication:

1. Duplication of fact

2. Duplication of logic

3. Duplication of structure

Duplication of fact

Duplication of fact is usually easy to see and fix. A common case is a “magic number” used by multiple parts of the code, such as a conversion factor or a maximum value. We saw this in an earlier example with the 21 days we used to calculate velocity. Another common example is a status variable that has only a few valid values, and the list of those values is duplicated: