Add implemented List functions

docs/functions/list_functions.md

@@ -1,2 +1,259 @@
 # List Functions 
 
+## Data Setup
+
+```
+SELECT * from cypher('graph_name', $$
+CREATE (A:Person {name: 'Alice', age: 38, eyes: 'brown'}),
+	(B:Person {name: 'Bob', age: 25, eyes: 'blue'}),
+	(C:Person {name: 'Charlie', age: 53, eyes: 'green'}),
+	(D:Person {name: 'Daniel', age: 54, eyes: 'brown'}),
+	(E:Person {name: 'Eskil', age: 41, eyes: 'blue', array: ['one', 'two', 'three']}),
+	(A)-[:KNOWS]->(B),
+	(A)-[:KNOWS]->(C),
+	(B)-[:KNOWS]->(D),
+	(C)-[:KNOWS]->(D),
+	(B)-[:KNOWS]->(E)
+$$) as (result agtype);
+```
+
+## keys
+
+keys returns a list containing the string representations for all the property names of a vertex, edge, or map.
+
+Syntax:`keys(expression)`
+
+Returns:
+```
+An Agtype list containing string agtype elements
+```
+
+Arguments:
+<table>
+  <tr>
+   <td>Name
+   </td>
+   <td>Description
+   </td>
+  </tr>
+  <tr>
+   <td>path
+   </td>
+   <td>An expression that returns a vertex, edge, or map.
+   </td>
+  </tr>
+</table>
+
+Considerations:
+* keys(null) returns null.
+
+Query:
+```
+SELECT * from cypher('graph_name', $$
+	MATCH (a)
+	WHERE a.name = 'Alice'
+	RETURN keys(a)
+$$) as (result agtype);
+```
+
+A list containing the names of all the properties on the vertex bound to a is returned.
+
+Result:
+
+
+<table>
+  <tr>
+   <td>keys
+   </td>
+  </tr>
+  <tr>
+   <td>["age", "eyes", "name"]</td>
+  </tr>
+  <tr>
+   <td colspan="1" >1 rows
+   </td>
+  </tr>
+</table>
+
+## range
+
+range() returns a list comprising all integer values within a range bounded by a start value start and end value end, where the difference step between any two consecutive values is constant; i.e. an arithmetic progression. The range is  inclusive, and the arithmetic progression will therefore always contain start and—depending on the values of start, step and end—end.
+
+Syntax:`range(start, end [, step])`
+
+Returns:
+```
+An Agtype list containing edge entities
+```
+
+Arguments:
+<table>
+  <tr>
+   <td>Name
+   </td>
+   <td>Description
+   </td>
+  </tr>
+  <tr>
+   <td>start
+   </td>
+   <td>An expression that returns an integer value.
+   </td>
+  </tr>
+  <tr>
+   <td>end
+   </td>
+   <td>An expression that returns an integer value.
+   </td>
+  </tr>
+  <tr>
+   <td>step
+   </td>
+   <td>A numeric expression defining the differencebetween any two consecutive values, with adefault of 1.
+   </td>
+  </tr>
+</table>
+
+Query:
+```
+SELECT *
+FROM cypher('graph_name', $$
+	RETURN range(0, 10), range(2, 18, 3)
+$$) as (no_step agtype, step agtype);
+```
+
+Two lists of numbers in the given ranges are returned.
+
+Result:
+<table>
+  <tr>
+   <td>no_step
+   </td>
+   <td>step
+   </td>
+  </tr>
+  <tr>
+   <td>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]</td>
+   <td>[2, 5, 8, 11, 14, 17]</td>
+  </tr>
+  <tr>
+   <td colspan="1" >1 row
+   </td>
+  </tr>
+</table>
+
+## labels
+
+labels returns a list containing the string representations for all the labels of a node.
+
+Syntax:`labels(vertex)`
+
+Returns:
+```
+An Agtype list containing String elements
+```
+
+Arguments:
+<table>
+  <tr>
+   <td>Name
+   </td>
+   <td>Description
+   </td>
+  </tr>
+  <tr>
+   <td>vertex
+   </td>
+   <td>An expression that returns a single vertex.
+   </td>
+  </tr>
+</table>
+
+Considerations:
+* labels(null) returns null.
+
+Query:
+```
+SELECT *
+FROM cypher('graph_name', $$
+	MATCH (a)
+	WHERE a.name = 'Alice'
+	RETURN labels(a)
+$$) as (edges agtype);
+```
+
+A list containing all the labels of the node bound to a is returned.
+
+Result:
+<table>
+  <tr>
+   <td>edges
+   </td>
+  </tr>
+  <tr>
+   <td>["Person"]
+   </td>
+  </tr>
+  <tr>
+   <td colspan="3" >1 row
+   </td>
+  </tr>
+</table>
+
+## relationships
+
+relationships() returns a list containing all the relationships in a path.
+
+Syntax:`relationships(path)`
+
+Returns:
+```
+An Agtype list containing edge entities
+```
+
+Arguments:
+<table>
+  <tr>
+   <td>Name
+   </td>
+   <td>Description
+   </td>
+  </tr>
+  <tr>
+   <td>path
+   </td>
+   <td>An expression that returns an Agtype path.
+   </td>
+  </tr>
+</table>
+
+Considerations:
+* relationships(null) returns null.
+
+Query:
+```
+SELECT *
+FROM cypher('graph_name', $$
+	MATCH p = (a)-[]->(b)-[]->(c)
+	WHERE a.name = 'Alice' AND c.name = 'Eskil'
+	RETURN relationships(p)
+$$) as (edges agtype);
+```
+
+A list containing all the edges in the path p is returned.
+
+Result:
+<table>
+  <tr>
+   <td>edges
+   </td>
+  </tr>
+  <tr>
+   <td>[{"id": 1125899906842640, "label": "KNOWS", "end_id": 844424930131989, "start_id": 844424930131988, "properties": {}}::edge, {"id": 1125899906842644, "label": "KNOWS", "end_id": 844424930131992, "start_id": 844424930131989, "properties": {}}::edge]
+   </td>
+  </tr>
+  <tr>
+   <td colspan="3" >1 row
+   </td>
+  </tr>
+</table>