# From Pine

A Pine indicator maps to an `fg.Indicator` and a Pine strategy to an `fg.Strategy`. The names differ more than the ideas: outputs replace `plot`, settings replace `input`, and the `ta` module carries the indicators you know.

## What is different

- **Forge works on whole arrays.** A Pine script runs once per bar and `close[1]` is the previous bar. A Forge `calculate` fills arrays, and a strategy's `compute` returns signals for every bar at once.
- **Closed bars only.** Pine recalculates the forming bar on every tick, so a value can change before the bar ends. Forge decides on closed bars.
- **No look-ahead switch.** A higher-timeframe series is visible only after its own bar has closed.
- **Missing values are NaN,** and `fg.nz` and `fg.isna` replace `nz` and `na`.

The [traps page](https://oathra.dev/docs/porting/pine/traps) lists the mistakes that cost the most.

## Then read

Start with [repainting and look-ahead](https://oathra.dev/docs/concepts/repainting-and-look-ahead), which names repainting as Pine does, and [bar close and fills](https://oathra.dev/docs/concepts/bar-close-and-fills).

## Name by name

[Every Pine name beside what you write in Forge](https://oathra.dev/docs/porting/pine/to-forge).