exercise 3.64
Duh - maybe I should have chosen a stream based instead of iterative approach to solve the problem about streams.
exercise 3.65
skipping a few exercises
exercise 3.69 - ultimately took eli's version

Mine /seemed/ to generate all the right values - but finding (3,4,5)
was hanging (i.e. taking longer than my patience (several 10s of
seconds)).

Eli's version however got to (3,4,5) pretty quickly.
exercise 3.70: weighted pairs
Eli points out original merge would get rid of duplicates. Here we can't really  filter them out

(just because (1, 2) and (2, 1) have hte same weight, doens't mean they
are duplicates)
cleaned up the code some
had breakthrough of combining the stream to its own cdr and then filtering.
exercise 3.71 was pretty easy after 3.71
I believe this answer is correct
exer 3.74 was easy because i already did this sort of thing before.
Section 3.5.3 completed

skipped two exercises due to apathy