We learn short circuits in our first programming courses. We need to remember why.
TL;DR: Be lazy when evaluating boolean conditions
Problems
Side effects
Biyection Fault
Performance issues
Solutions
- Use a short circuit instead of a complete evaluation
Context
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.
Sample Code
Wrong
<?
if (isOpen(file) & size(contents(file)) > 0)
// Full evaluation
// Will fail since we cannot retrieve contents
// from not open file
Right
<?
if (isOpen(file) && size(contents(file)) > 0)
// Short circuit evaluation
// If file is not open it will not get the contents
Detection
[X] Automatic
We can warn our developers when they use full evaluation.
Tags
- Boolean
Exceptions
Don't use short-circuit as an IF alternative.
if the operands have side effects, this is another code smell.
Conclusion
Most programming languages support short-circuits.
Many of them have it as the only option.
We need to favor these kinds of expressions.
Relations
More Info
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.
Bertrand Meyer
This article is part of the CodeSmell Series.
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