预订演示
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Set Traversal

ancestor

ancestor(count: number, source: set)

ancestor(value: string, source: set)

ancestor(count: number, value: string, source: set)

The 'ancestor' function traverses each node in a set up a number of parent nodes, excluding any nodes that fail the traversal. The number of nodes to traverse, the name of the target node for the traversal, or both can be provided as parameters.

  • When the number of nodes is provided, but the target node name is not, any nodes with the specified number of parents will pass the traversal; any node that runs out of parents will be dropped from the set
  • When the name of the target is specified, but the number of nodes to traverse is not, nodes with a parent with a matching name at any point in the hierarchy will pass the traversal; any node with no matching parent is excluded
  • When both the number of nodes and the target name are provided, only nodes that have a parent node with the specified name at the specified offset pass the traversal; all other nodes are removed from the set

It is possible - even likely - that these calls will generate sets having duplicate values. This is by design, as the concrete rules for sets do not define them as being discrete.  If (as in most cases) you want your set to be discrete, use the 'distinct' function described in the The mFQL Language Help topic.

This sample extracts a set of all nodes named 'OPERATION', then traverses each node up one level to its immediate parent. Any 'OPERATION' node with no parent is excluded.

ancestor(1, getByNode("OPERATION"))

This sample extracts a set of all nodes named 'OPERATION', then traverses each node up to the first 'CLASS' parent node. Any 'OPERATION' node with no 'CLASS' parent is excluded.

ancestor("CLASS", getByNode("OPERATION"))

This sample extracts a set of all nodes named 'OPERATION', then traverses each node up one level to its immediate parent. If the parent node is not a 'CLASS' node, or the node fails to traverse though a lack of parent nodes, it is excluded.

ancestor(1, "CLASS", getByNode("OPERATION"))

filter

filter(count: number, source: set)

filter(value: string, source: set)

filter(count: number, value: string, source: set)

The 'filter' function is the same as the 'ancestor' function, except that it does not modify nodes – it is non-destructive. If a node is unable to pass the specified traversal, it is removed from the set.  Nodes that pass the traversal are left in place, unmodified.

It is often desirable to filter a set by the current node name. This can be used to ensure that the nodes returned from a 'with' or 'find' call are of a particular node type.  This example returns all nodes with an attribute with the value of “CFoo”, where the resulting node is a “TYPE” node.

filter(0, “TYPE”, find(“CFoo”))

For more details on the use of the 'filter' function, see the 'ancestor' function.

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