Combinatorics Calculator (nCr/nPr/multinomial) 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

t6-066

Effect

Computation or source lookup only

Input and validation requirements

The specification exposes an undefined factorial domain at r>n and does not state required rejection behavior. It also lists permutations with repetition without giving its formula or an explicit convention selector, allowing the same nPr-looking input to produce different results.

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": {
    "operation": "nCr",
    "n": 0,
    "r": 0
  },
  "expected_outputs": {
    "coefficient": 1
  },
  "working": "0!/(0!·(0-0)!) = 0!/(0!·0!) = 1/(1·1) = 1. This checks the zero boundary and uses 0!=1."
}

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-tranche6/tranche6-results.json