https://github.com/jarohen/graph-zip

A zipper library for Clojure that navigates graph structures
https://github.com/jarohen/graph-zip

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A zipper library for Clojure that navigates graph structures

• Host: GitHub
• URL: https://github.com/jarohen/graph-zip
• Owner: jarohen
• Archived: true
• Created: 2012-06-27T10:25:30.000Z (over 12 years ago)
• Default Branch: master
• Last Pushed: 2012-09-16T13:11:09.000Z (about 12 years ago)
• Last Synced: 2024-08-12T07:59:36.876Z (3 months ago)
• Language: Clojure
• Size: 148 KB
• Stars: 19
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Graph-Zip

Graph zip is a zipper library for Clojure that can navigate graph

structures, with a similar syntax to xml-zip.

## Lein dependency:

    [graph-zip "0.5"]

## Usage

You can use graph zip like this:

### Building a graph

    ;; Dependencies for an in-memory graph

    (use 'graph-zip.core :only [graph-zip zip-> zip1-> zipper-node prop=])

    (use 'graph-zip.in-memory :only [build-in-memory-graph])

    ;; Build up the in-memory graph - a list of triples, each with a :subject, :property and :object

    (def my-map (build-in-memory-graph 

                  [{:subject "prod-host" :property :instance :object "prod-host/instance"}

                   {:subject "prod-host" :property :instance :object "prod-host/instance2"}

                   {:subject "prod-host" :property :instance :object "prod-host/instance3"}

                   {:subject "prod-host/instance" :property :userid :object "my-user"}

                   {:subject "prod-host/instance2" :property :userid :object "another-user"}

                   {:subject "prod-host/instance" :property "label" :object "1"}

                   {:subject "prod-host/instance2" :property "label" :object "2"}

                   {:subject "prod-host/instance" :property "cmdb:jvm" :object "prod-host/instance/jvm"}

                   {:subject "prod-host/instance/jvm" :property "cmdb:maxMem" :object "1024m"}]))

### Building a zipper

A zipper is a pair of the full graph, and the current node in the

traversal. We can build a re-usable zipper, rooted at the "prod-host"

node

    (def prod-host-zipper (graph-zip my-map "prod-host"))

This 'zips' along the ```:instance``` relation, and returns a list of

zippers.

Mapping zipper-node over the zippers returns just the nodes that are

related to "prod-host" by ```:instance```

    (zip-> prod-host-zipper

           :instance

           node) ;; -> ("prod-host/instance2" "prod-host/instance")

In a similar vein to xml-zip, you can prune the graph by using a

```prop=``` predicate.

If you are only expecting one result, you can use the ```zip1->``` function

instead.

    (zip1-> prod-host-zipper

            :instance

            (prop= "label" "2")

            node) ;; -> "prod-host/instance2"

Relations don't have to be keywords

    (zip1-> prod-host-zipper

            :instance

            [(prop= "label" "1")]

            "jvm"

            "maxMem"

            node) ;; -> "1024m"

Get the properties map of a node using ```props```

    (zip1-> prod-host-zipper

            :instance

            (prop= "label" "1")

            props) 

            ;; -> {"jvm" ("prod-host/instance/jvm"), 

                   "label" ("1"), 

                   :userid ("my-user")}

### Merging graphs

Graph-Zip can merge graphs from many sources. Here we are just merging

two in-memory graphs:

    (use 'graph-zip.merge-graph :only [make-merge-graph])

    (def additional-map 

     (build-in-memory-graph 

      [{:subject "prod-host" :property :instance :object "prod-host/instance3"}

       {:subject "prod-host" :property "cmdb:hostname" :object "prod-server.example.com"}

       {:subject "prod-host/instance3" :property :userid :object "my-user"}

       {:subject "prod-host/instance3" :property "label" :object "3"}]))   

                                                

    (def merged-graph (make-merge-graph my-map additional-map))

    (def merged-zipper (graph-zip merged-graph "prod-host"))

The merge behaves as you'd expect:

    (zip1-> merged-zipper

            :instance

            (prop= "label" "3")

            node) 

    ;; -> "prod-host/instance3"

    (zip1-> merged-zipper

            :instance

            (prop= "label" "1")

            node) 

    ;; -> "prod-host/instance"

    (zip-> merged-zipper

           :instance

           node)

    ;; -> ("prod-host/instance3" 

           "prod-host/instance2"

           "prod-host/instance")

### Traversing back up the graph

Since v0.3, it is possible to traverse back up the graph as well, with ```(incoming :property)```:

Find all the instances where the userid is ```my-user```:

```go-to``` moves the zipper to the given node.

    (zip-> merged-zipper

           (go-to "my-user")

           (incoming :userid))) 

    ;; -> ("prod-host/instance3" 

           "prod-host/instance")

                            

# Licence

Copyright (C) 2012 James Henderson, Malcolm Sparks

Distributed under the Eclipse Public License, the same as Clojure.