lee@rochester.UUCP (Lee Moore) (08/11/85)
Periodically there are requests on net.text for techniques to get a real
sorted index out of troff. Below is some stuff that I cooked up to
generate our graduate student handbook.
The plan is simple: use the ".tm" command of troff to write index items to
the standard error. Collect the standard error, sort it, process it and
feed it back into troff. At certain points, I will assume the use of the
-me macro package but this code should be generally useful. There are
two helper programs that are written in Icon which are included below.
I recommend the language Icon to any site that does alot of text processing.
First we have the index macro itself:
.de IN \" send an index entry to the stderr
.tm \\n%\t\\$1\t\\$2
..
It outputs the current page number and one or two arguments to the
standard error. The first argument is the major name and the second
is the minor name. The index will appear sorted first by major name and then
minor. Examples of usage:
.IN "Pet Licenses"
.IN "Shopping" "Food"
.IN "Shopping" "Clothes"
While running troff, one collects the standard error into a file. With the
Bourne shell this looks like:
troff -me files 2> files.ind
In the following examples we are going to the following output of stderr:
1 Shopping Food
2 Shopping Clothes
2 Shopping Food
3 Shopping Clothes
3 Shopping Food
4 Pet Licenses
4 Shopping Clothes
5 Pet Licenses
6 Pet Licenses
As a second step, the output is re-processed and feed back into troff:
sort +1n +0n -1n files.ind | fixindex | block | troff index.me
As you can see, two helper programs called fixindex and block were written.
The first program, deletes identical index entries that refer to the same
page, collects together all the page numbers that refer to the same index
item, and notes the breaks between major and minor items. Its output
is in the form of Troff macros calls. Applying sort and fixindex we get:
.I> "Pet Licenses" "4,5,6" <--- major heading
.Ib "Shopping" <--- start of minor headings
.I< "Shopping" "Clothes" "2,3,4"
.I< "Shopping" "Food" "1,2,3"
The following is source to fixindex.icn:
-----------------------------------------------------------------------
# transform raw index entries into new macros
#
# features include: merging page numbers and suppressing duplicates
# sorting out major headings from minor
#
# the (pre-sorted) input is of the form
# <page-number><tab><major name><tab><minor name>
#
record LineState(PageNum, Major, Minor)
procedure main()
local pageList, old, new
old := LineState()
new := LineState()
split(old) | return
pageList := old.PageNum
if null(old.Minor) fails then
write('.Ib "', old.Major, '"')
while split(new) do {
if old.Major == new.Major then
if old.Minor == new.Minor then {
if old.PageNum ~= new.PageNum then
pageList ||:= "," || new.PageNum }
else {
WriteEntry(old, pageList)
pageList := new.PageNum }
else {
WriteEntry(old, pageList)
pageList := new.PageNum
if null(new.Minor) fails then
write('.Ib "', new.Major, '"') }
AssignRecord(new, old) } # new -> old
WriteEntry(old, pageList)
end
procedure split(state)
static tabChar,
digits
initial { tabChar := cset("\t");
digits := cset("0123456789") }
scan read() | fail using {
state.PageNum := tab(many(digits))
tab(many(tabChar))
state.Major := tab(upto(tabChar)) | tab(0)
tab(many(tabChar))
state.Minor := tab(0) }
return
end
procedure WriteEntry(state, pageList)
if null(state.Minor) then
write('.I> "', state.Major, '" "', pageList, '"')
else
write('.I< "', state.Major, '" "', state.Minor,
'" "', pageList, '"')
end
procedure AssignRecord(a, b)
b.Major := a.Major
b.Minor := a.Minor
b.PageNum := a.PageNum
end
-----------------------------------------------------------------------
The program "block.icn" takes in the macros produced by the above program
and inserts a new macro where the first letter changes. This allows one
to break up the index into different sections for readability
.LB S
.Ib "Shopping" \" label a set of minor headings
.I< "Shopping" "Food" "1,2,3" \" a minor item macro call
.I< "Shopping" "Clothes" "2,3,4"
.LB P
.I> "Pet Licenses" "4,5,6" \" a major item macro call
The following is the source to block:
-----------------------------------------------------------------------
#
# Seperate index entries where the first letter of the entry
# changes. Produce a ".LB" at the break point. Provide
# the macro with the new letter
#
procedure main()
local doubleQuote,
line,
oldFirstChar,
firstChar
doubleQuote := cset('"')
oldFirstChar := ""
# read until end of file
while line := read() do {
scan line using {
tab(upto(doubleQuote)) | write("can't find double q")
move(1)
firstChar := &subject[&pos] }
# are the first two letters different?
if firstChar ~== oldFirstChar then {
write(".LB ", firstChar) }
oldFirstChar := firstChar
write(line) }
end
-----------------------------------------------------------------------
the following is the index macros that must be pre-pended to the output
of the block program.
-----------------------------------------------------------------------
. \" Macros for the index
.de Ib \" blank major entry
.br
.ne 2v
\\$1:
..
.de I> \" major entry
\\$1, \\$2
..
.de I< \" minor entry
.br
\\$2, \\$3
..
.de LB \" new letter starts here
.di DT \" start diverted text
.sp
.sz +2
.b
\\$1
.r
.sz -2
.sp
.di \" end diverted text
.ne \\n(dnu+1v \" get enough space for it
.DT \" output it
..
.\" set up various paramters for the right evironment.
.\" Your taste may be different.
.po 1.0i \" physical offset
.ta 5iR \" right alignment tab
.lp \" initialize -me
.nf
.ce
.sz 18
Index
.sp 1
.sz 10
.2c \" 2 column mode
.sp 3
--
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