place-right (<<)

The place-right operator >> is a path operator that is used to specify a particular path or node to appear at a specific location (of a path p to be discovered) from right to left.

Syntax

The syntax of << is as follows:

    << [index] node | << [index] (path)

The place-right operator can be applied on both a node or path. When it applies to a path, parentheses must be used. index here must be a non-negative integer. The place-right operator must appear in front of a node or a path. Hence, sometimes it is also referred as prefix path operator in Cyclone.

Scope

The right-place operator << can only be used in the goal section.

Semantics

A path s or node n is specified with << i indicates that s or n must appear at location i in p. i here specifies an index value of p. It starts from 0 to n, where n is the path length. The following diagram illustrate this index value.

The right most node in path is represented as an index value of 0, and the left most node is represented as an index value of n, where n is the path length. When the index value i is omitted, the default value 0 is assumed.

Example

 <<S1 && <<2(S3->S4)

Node S1 must appear at the end of a path and S3->S4 must appear at the 3rd node in a path(from right to left). Thus, a path S6->S3->S4->S5->S1 meets the above path condition.

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