YAMB: problems with yacc?

[Jay Maynard]

I tried entering the program hoc1, from the book _The Unix Programming
Environment_, and compiling it last night. It doesn't run: when fed an
expression like 2+2, instead of printing 4, it prints 2. It appears to
reproduce productions of the form:
expr: expr '+' expr { $$ = $1 + $3 }...
by simply returning $3, instead of computing the sum. I have checked the
program against the printed source in the book twice, and found no
errors. Neither yacc nor cc complain during compilation of the program.
I tried #defining YYDEBUG and setting yydebug to 1, but just got a lot
of output that I don't understand.
Am I bashing my head against YAMB (yet another Microport bug)?
Vitals: System V/AT (286) 2.3.0, plenty of (hard and ram-) disk.
I'd post the program here, to see if anyone else has the problem, but am
unsure of the legalities. (Any help here appreciated.)
The reason behind running a program that, according to its authors,
"provides about the same capabilities as a minimal pocket calculator,
and is substantially less portable"? I wanted to make sure I could make
it run before I went to the time and effort of keying in hoc6, the
full-featured version.

-- 
Jay Maynard, EMT-P, K5ZC...>splut!< | GEnie: JAYMAYNARD  CI$: 71036,1603
uucp: {uunet!nuchat,academ!uhnix1,{ihnp4,bellcore,killer}!tness1}!splut!jay
Never ascribe to malice that which can adequately be explained by stupidity.
The opinions herein are shared by none of my cats, much less anyone else.