foldBack

The original state if the option is None, otherwise it returns the updated state with the folder and the option value.

Type

type foldBack = <T, S>(folder: Folder<T, S>) => (option: Option<T>) => (state: S) => S

Examples

import {foldBack, Some} from 'fnxt/option';

const sum = foldBack((a:number, b:number) => a + b);
sum(Some(42))(1) // -> Some(43)
import {foldBack, None} from 'fnxt/option';

const sum = foldBack((a:number, b:number) => a + b);
sum(None)(1) // -> 1

See Also