fintech-algorithms
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Eligibility Screen

Install and import#

bash
npm install fintech-algorithms
ts
import { calculate } from "fintech-algorithms/index-and-benchmark-engineering/governance-and-maintenance/eligibility-screen";

Signature#

calculate(data)

Applies the qualification rules that decide what may be considered for membership at all — domicile, listing status, share class, and the rest. The first gate, and the one that defines what the index claims to represent.

Parameters#

NameTypeNotes
data{ candidates: Candidate[] }Each candidate carries the attributes the rules test. The rules travel with the data rather than being hard-coded, so a rule change is a data change.

Returns#

{ results, eligibleIds, rejectedCount }

A per-candidate result naming which rule rejected it — a rejection without a reason cannot be appealed or audited.

Errors#

  • When a candidate is missing an attribute a rule requires — recorded as a rejection reason rather than thrown

Complexity: time O(n × rules), space O(n).

Worked example#

verified This is the worked example published in the article, replayed by the test suite on every run. The output cannot drift.

Input#

data
{
  "candidates": [
    {
      "id": "A",
      "primaryListing": true,
      "eligibleType": true,
      "minPricePass": true,
      "historyPass": true
    },
    {
      "id": "B",
      "primaryListing": false,
      "eligibleType": true,
      "minPricePass": true,
      "historyPass": true
    },
    {
      "id": "C",
      "primaryListing": true,
      "eligibleType": true,
      "minPricePass": false,
      "historyPass": true
    }
  ]
}

Call#

calculate(data)

Returns#

object with 3 fields: results, eligibleIds, rejectedCount

{
  "results": [
    {
      "id": "A",
      "eligible": true,
      "reasons": []
    },
    {
      "id": "B",
      "eligible": false,
      "reasons": ["primaryListing"]
    },
    {
      "id": "C",
      "eligible": false,
      "reasons": ["minPricePass"]
    }
  ],
  "eligibleIds": ["A", "D"],
  "rejectedCount": 3
}

Diagrams#

Eligibility Screen — article hero
Eligibility Screen — failure guard
Eligibility Screen — worked example

Calculation flow#

Eligibility Screen calculation flow 
flowchart LR
    A["Point-in-time inputs"] --> B["Validate units and timing"]
    B --> C{"Contract feasible?"}
    C -->|No| D["Reject with reason"]
    C -->|Yes| E["Calculate Eligibility Screen"]
    E --> F["Recompute invariants"]
    F --> G{"Checks pass?"}
    G -->|No| D
    G -->|Yes| H["Publish audited output"]
Eligibility Screen methodology state 
stateDiagram-v2
    [*] --> FrozenInputs
    FrozenInputs --> Validated: contract passes
    FrozenInputs --> Rejected: missing or infeasible
    Validated --> Calculated: apply named rule
    Calculated --> Audited: invariants pass
    Calculated --> Rejected: invariant fails
    Audited --> Published: version and timestamp recorded
    Published --> Revised: approved correction
    Revised --> FrozenInputs: rebuild from retained source state

How it works#

This page states the contract — how to call it correctly. The article explains the concept: why it works, and where it breaks.

Read the article →

References#

The rest of the Governance and Maintenance family#