Abstract: Functional programming appears to be enjoying a renaissance of interest for developing practical, “real-world” applications. Proponents have long maintained that the functional style is a better way to modularize programs and reduce complexity. What is new in this paper is we test this claim by studying the complexity of open source codes written in Scala, a modern language that unifies functional and object programming. We downloaded from GitHub, Inc., a portfolio of mostly “trending” Scala repositories that included the Scala compiler and standard library, much of them written in Scala; the Twitter, Inc., server and its support libraries; and many other repositories, several of them production-oriented and commercially inspired. In total we investigated approximately 22,000 source files with 2 millions lines of code and 223,000 methods written by hundreds of programmers. To analyze these sources, we developed a novel compiler kit that measures lines of code and adaptively learns to estimate the cyclomatic complexity of functional-object codes. The data show, first, lines of code and cyclomatic complexity are positively correlated as we expected but only weakly which we did not expect with Kendall’s t=0.258–0.274. Second, 75% of the Scala methods are straight-line, that is, they have the lowest possible cyclomatic complexity. Third, nearly 70% of methods have three or fewer lines. Fourth, the distributions of lines of code and cyclomatic complexity are both non-Gaussian (P<0.01), which is as surprising as it is interesting. These data may offer new insights into software complexity and the large-scale structure of applications including but not necessarily limited to Scala.

Ron Coleman and Matthew A. Johnson, “A Study of Scala Repositories on Github” International Journal of Advanced Computer Science and Applications(IJACSA), 5(7), 2014. http://dx.doi.org/10.14569/IJACSA.2014.050721

@article{Coleman2014,
title = {A Study of Scala Repositories on Github},
journal = {International Journal of Advanced Computer Science and Applications},
doi = {10.14569/IJACSA.2014.050721},
url = {http://dx.doi.org/10.14569/IJACSA.2014.050721},
year = {2014},
publisher = {The Science and Information Organization},
volume = {5},
number = {7},
author = {Ron Coleman and Matthew A. Johnson}
}