Module Ordered

A module for adding getNext(), getPrevious() members to a type that is in some way orderable, in optional groups.

For instance, variables in a file may be ordered by their line number and grouped by their file.

To use this module, extend the class Ordered<T>::Type or Ordered<T>::GroupBy<G>::Type, where T is the type you want to order (for instance, a variable) and G is the optional type you want to group by (for instance, a file name). You must also implement the member predicate int getOrder() (items will be ordered by the result of this predicate) and if relevant, the member G getGroup().

The member getOrder() must not have duplicate values for two items within the same group to ensure correctness.

Example grouped usage:

class OrderedVar extends Ordered<Variable>::GroupBy<File>::Type {
  override int getOrder() { result = this.getLocation().getStartLine() }
  override File getGroup() { result = this.getFile() }
}

// Selects all variables in a file, along with the previous and next.
from OrderedVar v
select v.getName(), v.getPrevious().getName(), v.getNext().getName()

Example ungrouped usage:

class OrderedFib extends Ordered<int>::Type {
  OrderedFib() { this in fibonacciNumbers() }
  override int getOrder() { result = this }
}

from OrderedFib f
select f, f.getPrevious(), f.getNext()