Published in the Proceedings of VL 98, 1-4 September 1998 at Nova Scotia, Canada. Personal use of this material is permitted. Iteration, for instance, has been provided in different ways in several languages. The purpose of this paper is to give a contribution to the debate on data-flow VPL constructs. A typical case of parallel iteration is sequential access to all the elements of a data structure, so that certain operations can be performed on them.
Input ports are on the left side, while output ports are on the right side.
Such block is mostly used as the entry point of loop structures, thanks to its ability to accept both an initial input value and successive updatings of it. The signal emitted by block HEAD every time it is activated can be employed to create a synchronism with execution of possible other blocks which do not directly need data contained in the list being inspected. Such block has as input the list to be scanned and as output the current element, besides the control signals. The situation for the For loop construct, whose explicit and compact forms are shown in Figure 3, is analogous. IF is to be executed.