**protocol**

`zipperp`

¶

Zipper protocol.

**Author:**Paulo Moura

**Version:**1.0

**Date:**2019/1/20

**Compilation flags:**

`static`

**Dependencies:**

**Remarks:**

## Public predicates¶

`zip/2`

¶

Adds a zipper to a compound term holding a sequence of elements. Fails if the sequence is empty.

**Compilation flags:**

`static`

**Template:**

`zip(Sequence,Zipper)`

**Mode and number of proofs:**

`zip(+sequence,--zipper)`

- `zero_or_one`

`zip/3`

¶

Adds a zipper to a compound term holding a sequence of elements. Also returns the first element. Fails if the sequence is empty.

**Compilation flags:**

`static`

**Template:**

`zip(Sequence,Zipper,First)`

**Mode and number of proofs:**

`zip(+sequence,--zipper,--term)`

- `zero_or_one`

`unzip/2`

¶

Removes a zipper from a sequence.

**Compilation flags:**

`static`

**Template:**

`unzip(Zipper,Sequence)`

**Mode and number of proofs:**

`unzip(@zipper,--sequence)`

- `one`

`current/2`

¶

Current element.

**Compilation flags:**

`static`

**Template:**

`current(Zipper,Current)`

**Mode and number of proofs:**

`current(+zipper,?term)`

- `zero_or_one`

`next/2`

¶

Moves to the next element. Fails if already at the last elements.

**Compilation flags:**

`static`

**Template:**

`next(Zipper,NewZipper)`

**Mode and number of proofs:**

`next(+zipper,--zipper)`

- `zero_or_one`

`next/3`

¶

Moves to and returns the next element. Fails if already at the last elements.

**Compilation flags:**

`static`

**Template:**

`next(Zipper,NewZipper,Next)`

**Mode and number of proofs:**

`next(+zipper,--zipper,-term)`

- `zero_or_one`

`previous/2`

¶

Moves to the previous element. Fails if already at the first elements.

**Compilation flags:**

`static`

**Template:**

`previous(Zipper,NewZipper)`

**Mode and number of proofs:**

`previous(+zipper,--zipper)`

- `zero_or_one`

`previous/3`

¶

Moves to and returns the previous element. Fails if already at the first element.

**Compilation flags:**

`static`

**Template:**

`previous(Zipper,NewZipper,Previous)`

**Mode and number of proofs:**

`previous(+zipper,--zipper,-term)`

- `zero_or_one`

`rewind/2`

¶

Rewinds the zipper so that the first element becomes the current element.

**Compilation flags:**

`static`

**Template:**

`rewind(Zipper,NewZipper)`

**Mode and number of proofs:**

`rewind(+zipper,--zipper)`

- `one`

`rewind/3`

¶

Rewinds the zipper so that the first element becomes the current element. Also returns the first element.

**Compilation flags:**

`static`

**Template:**

`rewind(Zipper,NewZipper,First)`

**Mode and number of proofs:**

`rewind(+zipper,--zipper,?term)`

- `zero_or_one`

`forward/2`

¶

Forward the zipper so that the last element becomes the current element.

**Compilation flags:**

`static`

**Template:**

`forward(Zipper,NewZipper)`

**Mode and number of proofs:**

`forward(+zipper,--zipper)`

- `one`

`forward/3`

¶

Forward the zipper so that the last element becomes the current element. Also returns the last element.

**Compilation flags:**

`static`

**Template:**

`forward(Zipper,NewZipper,Last)`

**Mode and number of proofs:**

`forward(+zipper,--zipper,?term)`

- `zero_or_one`

`apply/2`

¶

Applies a closure to the current element.

**Compilation flags:**

`static`

**Template:**

`apply(Closure,Zipper)`

**Meta-predicate template:**

`apply(1,*)`

**Mode and number of proofs:**

`apply(+callable,+zipper)`

- `zero_or_more`

`insert_before/3`

¶

Inserts an element before the current one.

**Compilation flags:**

`static`

**Template:**

`insert_before(Zipper,Element,NewZipper)`

**Mode and number of proofs:**

`insert_before(+zipper,?term,--zipper)`

- `zero_or_one`

`insert_after/3`

¶

Inserts an element after the current one.

**Compilation flags:**

`static`

**Template:**

`insert_after(Zipper,Element,NewZipper)`

**Mode and number of proofs:**

`insert_after(+zipper,?term,--zipper)`

- `zero_or_one`

`replace/3`

¶

Replaces the current element with a new element.

**Compilation flags:**

`static`

**Template:**

`replace(Zipper,NewCurrent,NewZipper)`

**Mode and number of proofs:**

`replace(+zipper,?term,--zipper)`

- `one`

`delete_and_previous/2`

¶

Deletes the current element and moves to the previous element. Fails if no previous element exists.

**Compilation flags:**

`static`

**Template:**

`delete_and_previous(Zipper,NewZipper)`

**Mode and number of proofs:**

`delete_and_previous(+zipper,--zipper)`

- `zero_or_one`

`delete_and_next/2`

¶

Deletes the current element and moves to the next element. Fails if no next element exists.

**Compilation flags:**

`static`

**Template:**

`delete_and_next(Zipper,NewZipper)`

**Mode and number of proofs:**

`delete_and_next(+zipper,--zipper)`

- `zero_or_one`

`delete_and_unzip/2`

¶

Deletes the current element and removes the zipper returning the resulting sequence.

**Compilation flags:**

`static`

**Template:**

`delete_and_unzip(Zipper,Sequence)`

**Mode and number of proofs:**

`delete_and_unzip(+zipper,--sequence)`

- `one`

`delete_all_before/2`

¶

Deletes all elements before the current element.

**Compilation flags:**

`static`

**Template:**

`delete_all_before(Zipper,NewZipper)`

**Mode and number of proofs:**

`delete_all_before(+zipper,--zipper)`

- `one`

`delete_all_before_and_unzip/2`

¶

Deletes all elements before the current element and removes the zipper returning the resulting sequence.

**Compilation flags:**

`static`

**Template:**

`delete_all_before_and_unzip(Zipper,NewZipper)`

**Mode and number of proofs:**

`delete_all_before_and_unzip(+zipper,--sequence)`

- `one`

`delete_all_after/2`

¶

Deletes all elements after the current element.

**Compilation flags:**

`static`

**Template:**

`delete_all_after(Zipper,NewZipper)`

**Mode and number of proofs:**

`delete_all_after(+zipper,--zipper)`

- `one`

`delete_all_after_and_unzip/2`

¶

Deletes all elements after the current element and removes the zipper returning the resulting sequence.

**Compilation flags:**

`static`

**Template:**

`delete_all_after_and_unzip(Zipper,NewZipper)`

**Mode and number of proofs:**

`delete_all_after_and_unzip(+zipper,--sequence)`

- `one`

## Protected predicates¶

(none)

## Private predicates¶

(none)