TL;DR: Be lazy when evaluating boolean conditions
- Use a short circuit instead of a complete evaluation
We learn booleans in our 101 computer courses.
Boolean's truth tables are great for mathematics, but we need to be more intelligent as software engineerings.
Short circuit evaluation helps us to be lazy and even build invalid full evaluations.
if (isOpen(file) & size(contents(file)) > 0) // Full evaluation // Will fail since we cannot retrieve contents // from not open file
if (isOpen(file) && size(contents(file)) > 0) // Short circuit evaluation // If file is not open it will not get the contents
We can warn our developers when they use full evaluation.
Don't use short-circuit as an IF alternative.
if the operands have side effects, this is another code smell.
Most programming languages support short-circuits.
Many of them have it as the only option.
We need to favor these kinds of expressions.
Writing a class without its contract would be similar to producing an engineering component (electrical circuit, VLSI (Very Large Scale Integration) chip, bridge, engine...) without a spec. No professional engineer would even consider the idea.
This article is part of the CodeSmell Series.