Function computed

computed<T>(fn, options?): Computed<T>
Creates a new Computed instance. Computed is a reactive primitive that holds a value that is computed from other reactive values.
Type Parameters
- T
Parameters
- fn: (() => T)
  The function that returns the value of the Computed
  - - (): T
    - Returns T
- Optional options: {
      compareFunction: ((a, b) => boolean);
      isHardFunction: boolean;
      name: string;
  }
  Options
  - compareFunction: ((a, b) => boolean)
    A function that compares two values to determine if they are equal.
    - (a, b): boolean
      Parameters
      a: T
      b: T
      Returns boolean
  - isHardFunction: boolean
    Whether the function is a hard function. If true, it prevents calling the function by comparing the string representation of the dependencies.
  - name: string
    The name of Computed.
Returns Computed<T>
A new Computed instance with the given function and options.
Example
```
const a = atom(0);
const b = computed(() => a.value + 1);

b.subscribe(() => {
    console.log(b.value);
});

a.value = 1;
// b = 2
```
- Defined in src/api/api.js:586