Symbol manipulation by threaded lists

(:tefi,~(~ il i,~ col~junction with lhe functions-~[f/] and t[,~l, which give the /rausformations thai ~ under-2,1~{ I goes between the points S a,~d T respeclively and the exit. u~.l tO : eally, We h~ve most r[~] = [~rH[~I-' ~'[f,[~ll; T-~ s[fd~]]l Ill0r(, ~ti0ns~)8sell. in this } apu~a~ ;ider ~i, definil f that! s, fii~ii2 t ion ,eks g~ hat di) will i 4; Given a flowch'trt with a single, entrance and a single exit, it is easy ~(, write down the recursive function that gives the tr'msformation of tim state vector from entrance to exit in terms of the corresponding functions for the !4 ¸ computation blocks and the predicates of tile branch points. In general, we proceed as follows. In figure 6, let ~ be an n-way branch point, and let fi, ... , f, be the computations leading to branch points fl~, f12, ' " , fl .... l~et 4) be the function that transforms between fl and the exit of the chart, and let (b~ , • " • , 4,~ be the corresponding functions for f l ~ , .