# `combinations`

This library provides predicates for generating and querying combinations over lists. The following categories of predicates are provided:

- Generation operations - Predicates for generating combinations.

- Ordering variants - Predicates that support an additional order argument (`default`, `lexicographic`, or `shortlex`) for controlling output order.

- Distinct-value generation - Predicates for generating combinations while deduplicating equal-valued results.

- Indexed access - Predicates for direct access to combinations at specific positions, including distinct combinations.

- Counting operations - Predicates for counting combinations and distinct combinations.

- Random selection - Predicates for randomly selecting and sampling combinations and distinct combinations.

- Stepping operations - Predicates for moving to the next or previous combination in lexicographic order.

Dedicated `arrangements`, `cartesian_products`, `multisets`, `permutations`, `derangements`, `partitions`, and `subsequences` libraries are also available for focused APIs on related operations. The `multisets` library is the repetition-allowed counterpart to this library.

## API documentation

Open the ../../apis/library_index.html#combinations link in a web browser.

## Loading

To load all entities in this library, load the `loader.lgt` file:

    | ?- logtalk_load(combinations(loader)).

## Testing

To test this library predicates, load the `tester.lgt` file:

    | ?- logtalk_load(combinations(tester)).