Component programming with ranges

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2021-06-09 12:00:07

Component-style programming can be used to implement complex algorithms in a way that's straightforward to write, easy to read, and amenable to code reuse.

One of the more influential courses I took in college was on Jackson Structured Programming. It identified two sources of programming complexity (i.e., where bugs are most likely to occur): structure conflicts and writing loops.

Structure conflicts are mismatches between the structure of the program and the structure of the data, or mismatches between two or more data structures that must be processed simultaneously. For example, to read a text file formatted into lines, we may write a loop that reads each line in turn; however, the data in the file may be structured as a preamble, a body, and an epilogue. Since this structure is not reflected in the code, it often prompts programmers to introduce flags, state variables, and the like, in order to resolve the conflict between program structure and data structure. However, such ad hoc methods of resolving structure conflicts often increase the complexity of the code and the coupling between various parts of the code, making the code more fragile and prone to bugs.

Loops are a complex construct in imperative programming. One indication of how complex they can be is the fact that proving that a loop terminates at all is, in the general case, equivalent to solving the halting problem, which is unsolvable. This is especially true when the loop condition is complex. The difficulty is further compounded when nested loops are involved. Unfortunately, the ad hoc methods of resolving structure conflicts often increase the complexity of loop conditions and introduce nested loops, thus making the code doubly prone to bugs.