This is a little program that justifies the paragraphs read from STDIN and writes the result to STDOUT. It can be used as a filter from within VI, for instance.

[!] VersionNotice: The below code pertains to an older Lua version, Lua 4. It does not run as is under Lua 5.

-- easy queue implementation ------------------------------------------
function q_create()
 local q = {}
 q.first = 0
 q.last = 0
 return q
end
function q_insert(q, s)
 q[q.last] = s
 q.last = q.last + 1
end
function q_empty(q)
 return q.first >= q.last
end
function q_remove(q)
 if q_empty(q) then
 return nil
 end
 local s = q[q.first]
 q[q.first] = nil
 q.first = q.first+1
 return s
end
function q_card(q)
 return q.last - q.first
end
function q_length(q, f)
 local l, i = 0, q.first
 while i < q.last do
 l = l + strlen(q[i])
 i = i + 1
 end
 return l
end
-- line creation routines ------------------------------------------
-- justifies one line to fit into MAX columns 
function justify(q)
 local blanks = MAX - q_length(q)
 local skips = q_card(q) - 1
 local line = q_remove(q)
 local quotient = floor(blanks/skips)
 local reminder = blanks/skips - quotient
 local error = 0
 while skips > 0 do
 error = error + reminder
 if error >= 0.5 then
 error = error - 1
 line = line .. strrep(" ", quotient+1)
 else
 line = line .. strrep(" ", quotient)
 end
 line = line .. q_remove(q)
 skips = skips - 1
 end
 return line or ""
end
-- join all words with one space between them
function catenate(q)
 local line = q_remove(q)
 while not q_empty(q) do
 line = line .. " " .. q_remove(q)
 end
 return line or ""
end
-- main program -----------------------------------------------------
DEFMAX = 72
-- tries to get MAX from command-line
if not arg or getn(arg) < 1 then
 MAX = DEFMAX
else
 MAX = tonumber(arg[1])
 if not MAX or MAX < 0 then
 MAX = DEFMAX
 end
end
-- collects all text from stdin
text = q_create()
line = read()
while line do
 _, n = gsub(line, "(%S+)", function (s) q_insert(%text, s) end)
 if n == 0 then
 q_insert(text, "\n")
 end
 line = read()
end
-- justify paragraphs
line = q_create()
word = q_remove(text)
size = 0
while word do
 if word == "\n" then
 if not q_empty(line) then
 write(catenate(line), "\n\n")
 else
 write("\n")
 end
 size = 0
 elseif size + strlen(word) > MAX then
 write(justify(line), "\n")
 size = 0
 end
 if word ~= "\n" then
 q_insert(line, word)
 size = size + strlen(word) + 1
 end
 word = q_remove(text)
end
write(catenate(line), "\n")
	

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Last edited January 6, 2007 1:02 pm GMT (diff)