# Fx.filterMap

Maps and filters elements of an Fx in a single operation.

## Signatures

```ts
export declare const filterMap: {
    <A, B>(f: (a: A) => Option.Option<B>): <E, R>(self: Fx<A, E, R>) => Fx<B, E, R>;
    <A, E, R, B>(self: Fx<A, E, R>, f: (a: A) => Option.Option<B>): Fx<B, E, R>;
};
```

## Why

`filterMap` represents a partial synchronous transformation explicitly with `Option`. Each input
produces at most one output: `Some` is unwrapped and `None` is omitted, with source order intact.

## Ownership and lifetime

This operation is stateless and acquires no resources. It preserves the source's error and
service channels and stops whenever the source or consuming fiber stops.

## Examples

```ts
import { Fx } from "@typed/fx"
import { Option } from "effect"

const numbers = Fx.fromIterable(["1", "x", "2"]).pipe(
  Fx.filterMap((text) => Number.isNaN(Number(text)) ? Option.none() : Option.some(Number(text))),
)
```