Reordering Program Statements for Improving Readability

In order to understand source code, humans sometimes execute the program in their mind. When they illustrate the program execution in their mind, it is necessary to memorize what values all the variables are along with the execution. If there are many variables in the program, it is hard to their memorization. However, it is possible to ease to memorize them by shortening the distance between the definition of a variable and its reference if they are separated in the source code. This paper proposes a technique reordering statements in a module by considering how far the definition of a variable is from its references. We applied the proposed technique to a Java OSS and collected human evaluations for the reordered methods. As a result, we could confirm that the reordered methods had better readability than their originals. Moreover, we obtained some knowledge of human consideration about the order of statements.