/
Drop.ts
60 lines (55 loc) 路 1.45 KB
/
Drop.ts
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import {Tail} from './Tail'
import {Cast} from '../Any/Cast'
import {IterationOf} from '../Iteration/IterationOf'
import {Iteration} from '../Iteration/Iteration'
import {Way} from '../Iteration/_Internal'
import {List} from './List'
import {Pos} from '../Iteration/Pos'
import {Prev} from '../Iteration/Prev'
import {Prepend} from './Prepend'
import {Naked} from './_Internal'
import {Extends} from '../Any/Extends'
/**
* @hidden
*/
type DropForth<L extends List, N extends Iteration> = {
0: DropForth<Tail<L>, Prev<N>>
1: L
}[Extends<0, Pos<N>>]
/**
* @hidden
*/
type DropBack<L extends List, N extends Iteration, I extends Iteration = Prev<N>, LN extends List = []> = {
0: DropBack<L, N, Prev<I>, Prepend<LN, L[Pos<I>]>>
1: LN
}[Extends<-1, Pos<I>>]
/**
* @hidden
*/
type __Drop<L extends List, N extends Iteration, way extends Way> = {
'->': DropForth<L, N>
'<-': DropBack<L, N>
}[way]
/**
* @hidden
*/
export type _Drop<L extends List, N extends number, way extends Way = '->'> =
__Drop<Naked<L>, IterationOf<N>, way> extends infer X
? Cast<X, List>
: never
/**
* Remove `N` entries out of `L`
* @param L to remove from
* @param N to remove out
* @param way (?=`'->'`) from front: '->', from end: '<-'
* @returns [[List]]
* @example
* ```ts
* ```
*/
export type Drop<L extends List, N extends number, way extends Way = '->'> =
L extends unknown
? N extends unknown
? _Drop<L, N, way>
: never
: never