# \#append

**URL:** https://swi-prolog.discourse.group/tag/append/168.md

[Latest](https://swi-prolog.discourse.group/latest.md) · [Categories](https://swi-prolog.discourse.group/categories.md) · [Tags](https://swi-prolog.discourse.group/tags.md)

---

## [append(X, Y, Y) creates cyclic term](https://swi-prolog.discourse.group/t/append-x-y-y-creates-cyclic-term/6697)

<div class="topic-metadata">

**Author:** [@brebs](https://swi-prolog.discourse.group/u/brebs)\
**Replies:** 14\
**Last updated:** [July 19, 2023, 11:16pm UTC](https://swi-prolog.discourse.group/t/append-x-y-y-creates-cyclic-term/6697 "2023-07-19T23:16:34Z")

</div>

This creates a cyclic term: ?- append(X, Y, Y). X = \[\] ; X = \[\_A\], Y = \[\_A|Y\] ; X = \[\_A, \_B\], Y = \[\_A, \_B|Y\] ; Can be fixed with: append(L, R, A) :- ( R == A -\> L = \[\], % Loop through lengths of R …