Franklyn Turbak. 
<b>Synchronized Lazy Aggregates</b>. 
Draft of a technical memo based on my January 1994 MIT doctoral
dissertation. December 1, 1993.<hr>We present a new solution to the problem of expressing single-pass,
space-efficient list and tree computations in a modular fashion.
<i>synchronized lazy aggregates</i> augment existing methods for expressing
programs as networks of operators acting on aggregate data, but
overcome many limitations.  The technique is based on a dynamic model
of lock step processing that enables the operators in a network to
simulate the operational behavior of a monolithic loop or recursion.
The key to the technique is the <i>synchron</i>, a new first-class object
that allows concurrently executing operators to participate in a
barrier synchronization. We describe the design of synchronized lazy
aggregates and present examples of their implementation and use.<hr>[<a href="slag.ps">PS</a>]  [<a href="slag.pdf">PDF</a>]