Documentation Index
Fetch the complete documentation index at: https://mehen.ophi.dev/llms.txt
Use this file to discover all available pages before exploring further.
The ABC metric is a size measure proposed by Jerry Fitzpatrick in 1997. It counts three types of
syntactic features and reports them as a vector and as a magnitude.
| Letter | What it counts |
|---|
| Assignments | Variable assignments (=, +=, −=, ++, −−, etc.). |
| Branches | Calls to other procedures (i.e., method/function invocations). |
| Conditions | Conditional tests (if, case, when, ternary, exception catches, comparison |
| operators). | |
<A, B, C> is reported alongside the magnitude |ABC| = sqrt(A² + B² + C²).
What mehen emits
| Key | Type | Description |
|---|
abc | float | Magnitude sqrt(A² + B² + C²). |
abc.assignments | int | Total assignments in the space. |
abc.assignments_min | int | Minimum across child spaces. |
abc.assignments_max | int | Maximum across child spaces. |
abc.assignments_average | float | Average across child spaces. |
abc.branches | int | Total branches. |
abc.branches_min / _max / _average | — | Aggregates. |
abc.conditions | int | Total conditions. |
abc.conditions_min / _max / _average | — | Aggregates. |
How to read it
There is no universal threshold, but Fitzpatrick’s original paper proposed:
| Magnitude | Interpretation |
|---|
| 0–10 | Tiny method; check whether it should be inlined. |
| 10–20 | Normal method size. |
| 20–40 | Large; consider refactoring. |
| 40+ | Very large; refactor candidate. |
rubocop-rubycop/rubycritic, which uses
<A, B, C> and a magnitude threshold of 17 by default for methods.
Per-language increments
Each language analyzer maps its statement and expression node kinds onto the three buckets. The
canonical mapping:
- Assignments:
=, +=, −=, *=, /=, %=, <<=, >>=, &=, |=, ^=, prefix/postfix
++/−−, parameter default values where applicable.
- Branches: function calls, method calls, constructors,
super(...) calls, and dynamic dispatch.
- Conditions:
if, else if, case/when, ternary, && / ||, equality and ordering operators,
exception handlers (catch, rescue, except).
References
See also
