Summation & Product Notation Evaluator 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

t4-021

Effect

Computation or source lookup only

Input and validation requirements

The evaluator has an undefined-result failure mode when an expression such as 1/k includes k=0; it must reject the input instead of producing a numeric result. Geometric closed-form evaluation also requires a separate r=1 branch because the ordinary formula divides by 1-r.

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": "sum",
    "expression": "k",
    "index": "k",
    "lower_bound": 1,
    "upper_bound": 10
  },
  "expected_outputs": {
    "numeric_total": 55,
    "closed_form_match": true,
    "closed_form": "N(N+1)/2"
  },
  "working": "Direct sum: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55. Closed form with N = 10: N(N+1)/2 = 10×11/2 = 110/2 = 55."
}

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