Unit Price / Best-Value Comparator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t5-082

Effect

Computation or source lookup only

Input and validation requirements

A zero quantity produces an undefined division, and mixed units require an explicitly defined normalization branch. Without validation and unit conversion, the comparator can produce undefined results or an incorrect ranking.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "options": [
      {
        "id": "A",
        "price": 5.98,
        "quantity": 2,
        "unit": "L"
      },
      {
        "id": "B",
        "price": 3.29,
        "quantity": 1,
        "unit": "L"
      }
    ],
    "target_unit": "L",
    "currency": "USD"
  },
  "expected_outputs": {
    "unit_prices": [
      {
        "id": "A",
        "price_per_unit": 2.99,
        "unit": "USD/L"
      },
      {
        "id": "B",
        "price_per_unit": 3.29,
        "unit": "USD/L"
      }
    ],
    "ranked_best_value": [
      "A",
      "B"
    ]
  },
  "working": "A: 5.98 USD / 2 L = 2.99 USD/L. B: 3.29 USD / 1 L = 3.29 USD/L. Since 2.99 < 3.29, ranking is A first, then B."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche5/tranche5-results.json