object

# `halstead_metric(Stroud)`

- `Stroud` - Coeficient for computing the time required to program.

Computes Halstead complexity numbers for an entity.

Author: Paulo Moura
Version: 0.7
Date: 2018/7/18
Compilation flags:
`static, context_switching_calls`
Imports:
`public` code_metrics_utilities
`public` code_metric

## Public interface

(see related entities)

## Protected interface

(see related entities)

## Private predicates

(see related entities)

## Operators

(none)

## Remarks

- Definition of operators: Predicates declared, user-defined, and called are interpreted as operators. Built-in predicates and built-in control constructs are ignored.
- Definition of operands: Predicate arguments are abstracted and interpreted as operands. Note that this definition of operands is a significant deviation from the original definition, which used syntactic literals.
- Pn: Number of distinct predicates (declared, defined, called, or updated)
- PAn: Number of predicate arguments (assumed distinct)
- Cn: Number of predicate calls/updates + number of clauses
- CAn: Number of predicate call/update arguments + number of clause head arguments
- EV: Entity vocabulary: EV = Pn + PAn
- EL: Entity length: EL = Cn + CAn
- V: Volume: V = EL * log2(EV)
- D: Difficulty: D = (Pn/2) * (CAn/An)
- E: Effort: E = D * V
- T: Time required to program: T = E/k seconds (k is the Stroud number; defaults to 18)
- B: Number of delivered bugs: B = V/3000
- Entity score: Represented as the compound term pn_pan_cn_can_ev_el_v_d_e_t_b/11.