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docs/content/en/functions/intersect.md

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+---
+title: intersect
+linktitle: intersect
+description: Returns the common elements of two arrays or slices.
+godocref:
+date: 2017-02-01
+publishdate: 2017-02-01
+lastmod: 2017-02-01
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: []
+signature: ["intersect SET1 SET2"]
+workson: []
+hugoversion:
+relatedfuncs: []
+deprecated: false
+aliases: []
+---
+
+The elements supported are strings, integers, and floats (only float64).
+
+A useful example of `intersect` functionality is a "related posts" block. `isset` allows us to create a list of links to other posts that have tags that intersect with the tags in the current post.
+
+The following is an example of a "related posts" [partial template][partials] that could be added to a [single page template][single]:
+
+{{< code file="layouts/partials/related-posts.html" download="related-posts.html" >}}
+<ul>
+{{ $page_link := .Permalink }}
+{{ $tags := .Params.tags }}
+{{ range .Site.Pages }}
+    {{ $page := . }}
+    {{ $has_common_tags := intersect $tags .Params.tags | len | lt 0 }}
+    {{ if and $has_common_tags (ne $page_link $page.Permalink) }}
+        <li><a href="{{ $page.Permalink }}">{{ $page.Title }}</a></li>
+    {{ end }}
+{{ end }}
+</ul>
+{{< /code >}}
+
+This is also very useful to use as `AND` filters when combined with where:
+
+```
+{{ $pages := where .Site.RegularPages "Type" "not in" (slice "page" "about") }}
+{{ $pages := $pages | union (where .Site.RegularPages "Params.pinned" true) }}
+{{ $pages := $pages | intersect (where .Site.RegularPages "Params.images" "!=" nil) }}
+```
+
+The above fetches regular pages not of `page` or `about` type unless they are pinned. And finally, we exclude all pages with no `images` set in Page params.
+
+See [union](/functions/union) for `OR`.
+
+
+[partials]: /templates/partials/
+[single]: /templates/single-page-templates/