# Inside/Outside Bar Structure

`D08-F07-A17` · Geometric Chart Patterns → Market Structure, Breakouts, and Regimes · archetype `record-transform` · difficulty 2/5 · verification **verified**

Full page: https://docs.thefintechbuilder.com/geometric-chart-patterns/market-structure-breakouts-and-regimes/inside-outside-bar-structure/
Agent skill: `npx skills add IslamBaraka90/Fintech-Algorithms-Library` — https://docs.thefintechbuilder.com/guides/agent-skill/

## Install and import

```bash
npm install fintech-algorithms
```

```ts
import { insideOutsideBarStructure } from "fintech-algorithms/geometric-chart-patterns/market-structure-breakouts-and-regimes/inside-outside-bar-structure";
```

## Signature

```ts
insideOutsideBarStructure(input)
```

Classifies each bar against its immediate predecessor as `inside` (high not above and low not below), `outside` (high not below and low not above), or `neither`. A bar that exactly repeats the previous range is classified `inside`, because that test is evaluated first.

## Parameters

| Name | Type | Required | Notes |
| --- | --- | --- | --- |
| `input` | `TopicInput` | yes | `bars` is the required OHLCV history, strictly ordered by `timestamp` and on a single adjustment basis. This topic reads no keys from `parameters`; `period` (default `20`, integer of at least 2) is validated by the family but unused here. |

## Returns

`TopicResult`

`series` and `latest` carry a single string series, `structure`. The warm-up is one bar, since index 0 has no predecessor to compare against, so `ready_at` is 1.

## Warm-up

The first `1 bar` positions are `null`. Index 0 is null; every index from 1 onward carries one of `inside`, `outside` or `neither` and is never null.

## Errors

- When a bar's `high` is below its own `open`, `close`, or `low` (or `low` is above them) — throws Error
- When `bars` is empty or is not an array — throws Error

## Complexity

Time `O(n)`, space `O(n)`.

## Worked example

Captured by running this function on the input its own test provides. Real output of real code — but not asserted against a published figure.

### Input

`input`:

```json
{
  "bars": [
    {
      "timestamp": "2024-01-02",
      "basis": "synthetic-unadjusted",
      "open": 100,
      "high": 101.45,
      "low": 98.695,
      "close": 100,
      "volume": 750000,
      "benchmark": 200
    },
    {
      "timestamp": "2024-01-03",
      "basis": "synthetic-unadjusted",
      "open": 101.49111452,
      "high": 103.38381693,
      "low": 100.05480022,
      "close": 101.78791214,
      "volume": 795117,
      "benchmark": 200.56326135
    },
    {
      "timestamp": "2024-01-04",
      "basis": "synthetic-unadjusted",
      "open": 102.45519048,
      "high": 104.6701838,
      "low": 100.91147007,
      "close": 102.9549389,
      "volume": 840234,
      "benchmark": 201.11020913
    }
  ],
  "parameters": {}
}
```

### Call

```ts
insideOutsideBarStructure(input)
```

### Returns

object with 9 fields: topic_id, title, state, ready, ready_at, series, latest, parameters, …

```json
{
  "topic_id": "D08-F07-A17",
  "title": "Inside/Outside Bar Structure",
  "state": "calculated",
  "ready": true,
  "ready_at": 1,
  "series": {
    "structure": [null, "neither", "neither", "neither", "neither", "neither"]
  },
  "latest": {
    "structure": "neither"
  },
  "parameters": {},
  "diagnostics": {
    "causal": true,
    "input_count": 96
  }
}
```

## Verification and provenance

Tier: **verified** (via E).

The worked example below is the figure published in this algorithm's article, replayed and asserted by the test suite on every build. The arithmetic cannot drift without the build failing.

Both tiers guarantee the signature. Full explanation: https://docs.thefintechbuilder.com/guides/verification/

Generated from the docs.json payload shipped inside fintech-algorithms@0.13.0.
The signature and parameter list are checked against the compiled implementation at build time,
so a description that contradicts the code fails the build rather than reaching this file.

## Links

- Article (how it works, step by step): https://thefintechbuilder.com/geometric-chart-patterns/market-structure-breakouts-and-regimes/inside-outside-bar-structure/
- Implementation source: https://github.com/IslamBaraka90/Fintech-Algorithms-Library/blob/main/src/geometric-chart-patterns/market-structure-breakouts-and-regimes/inside-outside-bar-structure/impl.ts
- Package on npm: https://www.npmjs.com/package/fintech-algorithms
- Domain index for agents: https://docs.thefintechbuilder.com/geometric-chart-patterns/llms.txt