-ms accent bug

[Mark Turner]

Apparently, in 1983 the -ms macros were revised to
include a .AM macro which, when placed at the head of
a file to be formatted by nroff/troff, allowed one to use 
various new accents and characters.  /usr/lib/tmac/tmac.s
on our 4.2 system contains the lines
.de AM
.so \*(\\s.acc
..
meaning, I take it, read and use /usr/lib/ms/s.acc.
Now, our /usr/lib/ms/s.acc contains the line

.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'

This should mean that when one types \*(d- in a file sent through
n/troff, n/troff understands it as a lower case "eth", a character in Old
English.  The eth should look something like a partial-differential
sign with a dash through the stem.  The problem is: this line causes
troff to print the partial-differential-sign, and then backspace TWICE
to print a dash, and then proceed.  It should only backspace ONCE.
The result is: the dash occurs one character before it should, and
the character that should succeed the eth is printed on top of the
partial-differential sign.  I am too stupid to read the above code.
Can anyone tell me how to alter it so that the partial-differential
sign and the dash are overstruck?
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