2D Shape Area/Perimeter Calculator 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

t4-165

Effect

Computation or source lookup only

Input and validation requirements

• Division by zero is not inherent in the listed formulas, but any future formulas using an apothem, height, radius, or other denominator must reject zero denominators.
• Negative radii, negative lengths, invalid polygon vertex lists, fewer than three polygon vertices, and non-finite numeric inputs require validation.
• Self-intersecting polygon vertices can produce an algebraic shoelace result that is not the intended geometric area; this case needs an explicit policy.
• A sector angle outside the valid range for the intended sector representation, such as an angle greater than 360 degrees, needs validation or a defined interpretation.
• Ellipse perimeter requires an approximation or numerical method; labeling it as exact without qualification would be misleading.

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": {
    "shape": "circle",
    "radius": 5,
    "length_unit": "cm"
  },
  "expected_outputs": {
    "area": 78.53981633974483,
    "perimeter": 31.41592653589793,
    "area_unit": "cm²",
    "perimeter_unit": "cm"
  },
  "working": "Area = πr² = π × 5² = 25π = 78.53981633974483 cm². Perimeter = 2πr = 2 × π × 5 = 10π = 31.41592653589793 cm."
}

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-tranche4/tranche4-results.json