Linda is a generative communication coordination language, providing communication via tuple spaces (bags of tuples), where tuples may be read/removed from tuple spaces and inserted into them. Case base retrieval is used for case based reasoning (CBR) to retrieve solutions to problems from a set of previously encountered problems and their solutions, or retrieve matching solutions given a template of a desired solution. In implementing case base retrieval in Linda, closure has been identiied as a generic operation, generalising computation patterns in this application, illustrated here in terms of Linda instructions. The operational semantics of closure are speciied in terms of the Chemical Abstract Machine (CHAM) used to specify Liam, the Linda Abstract Machine. This speciication is reened in the CHAM to provide the basis for an eecient and parallel implementation of closure as a primitive instruction in Linda, increasing the performance of case base retrieval in Linda. Furthermore, closure is an instance of the Iterative Combination algorithmic skeleton , itself an instance of the Iterative Transformation algorithmic skeleton. This suggests the addition of Iterative Transformation to the basic classiication of algorithmic skeletons, having previously been omitted.