Re: elseifs and the fact that assignmens are not expressions
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- Subject: Re: elseifs and the fact that assignmens are not expressions
- From: Flemming Madsen <lua@...>
- Date: 2007年1月24日 11:30:35 +0100
OK. I found a way to do this.
Just a few thoughts
The lack of assignment capability can be ameliorated by moving
assignments in to a function.
Return values can then be made by assigning to table fields.
Some kind of slicing capability on return lists would have been nice.
Something along the lines of
ret.start, ret.stop, ret[] = string.find(...)
or some other way to specify that "ret" should suck up all remaining
return values into a list
Instead i had to make do with some rather ugly assign/shift loops as can
be seen in the attachment
Of course I also had to modify the main read loop, but this is covered
in other list topics
(http://lua-users.org/lists/lua-l/2001-03/msg00159.html)
/Flemming
Flemming Madsen wrote:
Hello
I was contemplating a small lua exercise, a program for listing my
currently vim'ed files a'la
local s,e,c,r,line,file,modified,pid,running
local fd = io.popen("sh -c 'vi -r 2>&1'", "r")
while (line = fd:read("*line")) do
^^^^^^
if s,e,c = string.find(line, "^ *file name: ([%w%p]*)") then
^^^^^^^^
file = c
elseif s,e,c = string.find(line, "^ *modified: (%a*)") then
^^^^^^^^
modified = c ~= "no"
elseif s,e,c,r = string.find(line, "^ *process ID: (%d*)(.*)") then
^^^^^^^^^
pid = c
running = string.find(r, "(still running)", 1, true) ~= nil
if file && modified then
io.write(string.format("%d %8d%s %s", modified and 1 or 0,
pid, running and "*" or " ", file)
end
file = nil
running = nil
end
end
fd:close()
Obviously this will not work, since assignments are not expressions in
lua,
nor is there any way of embedding assignment in expressions
Is there an easy way around this that i missed. Is this even a
candidate for the FAQ
Best /Flemming*
*
#!/usr/bin/env lua
local line,file,modified,pid,running
function findandset(line, pattern, ret)
-- ret = {}; wont work as the reference is by value
for k in pairs(ret) do ret[k] = nil end
local t = {string.find(line, pattern)}
if not t[1] then return nil end
ret.start = t[1]
ret.stop = t[2]
local i=3
while t[i] do ret[i-2] = t[i]; i=i+1 end
--DEBUG for k,v in pairs(ret) do print(k, "=", v) end
return ret
end
-- Make sure t is a table
local t = {}
local fd = io.popen("sh -c 'vi -r 2>&1'", "r")
while true do
line = fd:read("*line")
if not line then break end
if findandset(line, "^ *file name: ([%w%p]*)", t) then
file = t[1]
elseif findandset(line, "^ *modified: (%a*)", t) then
modified = t[1] ~= "no"
elseif findandset(line, "^ *process ID: (%d*)(.*)", t) then
pid = t[1]
running = string.find(t[2], "(still running)", 1, true) ~= nil
if file and modified ~= nil then
io.write(string.format("%d %8d%s %s\n", modified and 1 or 0,
pid, running and "*" or " ", file))
end
file = nil
running = nil
end
end