Absolute Priority Premise (APP)
Objective heuristic for comparing code quality by assigning mass values to code components. Lower total mass indicates simpler code.
The Six Components
| Component | Mass | Examples | |-------------|------|-------------------------------------| | Constant | 1 | 5, "hello", true, [] | | Binding | 1 | amount, userName, result | | Invocation | 2 | calculate(), Math.max(a, b) | | Conditional | 4 | if, switch, case, ?: | | Loop | 5 | while, for, forEach, map | | Assignment | 6 | x = 5, count++, list.add() |
Calculation
Total Mass = (constants x 1) + (bindings x 1) + (invocations x 2)
+ (conditionals x 4) + (loops x 5) + (assignments x 6)Lower mass = Better code (all else being equal).
Special Counting Rules
- Method declarations count as Constant (1) + Binding (1)
- Class definitions count as Constant (1) + Binding (1) (usually ignored in comparisons)
finalfields and local variables are Bindings (1), not Assignments (6)- Only re-assignments that modify values count as Assignment (6)
Integration with TDD
- Red Phase: Mass is irrelevant (focus on passing tests)
- Green Phase: Minimal code naturally has low mass
- Refactor Phase: Use APP to guide toward simpler solutions
Integration with Simple Design
- Tests Pass (Rule #1) - Always highest priority
- Reveals Intent (Rule #2) - May increase mass for clarity
- No Duplication (Rule #3) - Extract to reduce mass
- Fewest Elements (Rule #4) - Aligns with low mass goal
Simple Design Rule #2 trumps APP - Choose clarity over low mass. APP helps choose between equivalent clear solutions.
When to Apply
- During refactoring to choose between working solutions
- When comparing algorithms of similar functionality
- To guide toward simpler implementations
When NOT to Apply
- Never sacrifice clarity for lower mass
- Do not optimize prematurely based on mass alone
- Performance requirements may override mass considerations
- Domain complexity may require higher mass solutions
Limitations
- Not a direct indication of readability
- Ignores performance characteristics
- Validity unclear for general-purpose code (best for algorithm comparisons)
- Favors functional programming due to loop/assignment penalties
- The best specific mass values are unknown; these are Micah's suggested weights