Symbol manipulation by threaded lists
Alan J. Perlis, Charles A. Thornton · Communications of the ACM · 1960
Given a flowchart with a single entrance and a single exit, it is easy to write down the recursive function that gives the transformation of the state vector from entrance to exit in terms of the corresponding functions for the computation blocks and the predicates of the branch points.In general, we proceed as follows.In figure 6, let fJ be an n-way branch point, and let f 1 , • •, , f n be the computations leading to branch points P1 , f3t , • • • , f1n .Let q, be the function that transforms � hetween fJ and the exit of the chart, and let 'Pi , • • • , 4'n be the corresponding functions for f31 , • • • , {3 •• We then write q,{fl = lP1IEl -c/>1(f1Wl; . . .j Pn[!] -4'n[ f n[tlll AcknowledgmentsThe inadequacy of the >.-notation for naming recursive functions was noticed by N. Rochester, and he discovered an alternative to the solution involving label which has been used here.The form of subroutine for cons which permits its composition with other functions was invented, in connection with another programming system, by C. Gerberick and H. L.