[TUHS] BTL summer employees

arnold at skeeve.com arnold at skeeve.com
Mon Aug 3 19:24:34 AEST 2020

Doug McIlroy <doug at cs.dartmouth.edu> wrote:

> >> Even high-school employees could make lasting contributions.  I am
> >> indebted to Steve for a technique he conceived during his first summer
> >> assignment: using macro definitions as if they were units of associative
> >> memory. This view of macros stimulated previously undreamed-of uses.
> > Can you give some examples of what this looked like?
> One useless, but telling, program of mine was a Turing-machine
> simulator. Tape cells were represented by macros that contained
> a symbol and the (macro) names of adjacent cells. New cells
> could be generated as needed, with names derived from a counter.
> A natural way to store the state-transition table (I forget
> how it was actually done) would be as macros whose names
> are the concatenation of state and symbol names.
> Path-compression as used in union-find algorithms originated
> in a macroprocessor implementation by Bob Morris. Each graph
> node was represented by a macro that pointed to or toward
> the root of a tree spanning its graph component.

Thanks Doug.

I have to admit, I didn't really grok this.  My mental processes
seem to have frozen somewhat and I need to see something like this
in code before I really understand it. :-)



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