I see several posts about making a string in to a lua table, but my problem is a little different [I think] because there is an additional dimension to the table.
I have a table of tables saved as a file [i have no issue reading the file to a string].
let's say we start from this point:
local tot = "{{1,2,3}, {4,5,6}}"
When I try the answers from other users I end up with:
local OneDtable = {"{1,2,3}, {4,5,6}"}
This is not what i want.
how can i properly create a table, that contains those tables as entries?
Desired result:
TwoDtable = {{1,2,3}, {4,5,6}}
Thanks in advance
You can use the load function to read the content of your string as Lua code.
local myArray = "{{1,2,3}, {4,5,6}}"
local convert = "myTable = " .. myArray
local convertFunction = load(convert)
convertFunction()
print(myTable[1][1])
Now, myTable has the values in a 2-dimensional array.
For a quick solution I suggest going with the load hack, but be aware that this only works if your code happens to be formatted as a Lua table already. Otherwise, you'd have to parse the string yourself.
For example, you could try using lpeg to build a recursive parser. I built something very similar a while ago:
local lpeg = require 'lpeg'
local name = lpeg.R('az')^1 / '\0'
local space = lpeg.S('\t ')^1
local function compile_tuple(...)
return string.char(select('#', ...)) .. table.concat{...}
end
local expression = lpeg.P {
'e';
e = name + lpeg.V 't';
t = '(' * ((lpeg.V 'e' * ',' * space)^0 * lpeg.V 'e') / compile_tuple * ')';
}
local compiled = expression:match '(foo, (a, b), bar)'
print(compiled:byte(1, -1))
Its purpose is to parse things in quotes like the example string (foo, (a, b), bar) and turn it into a binary string describing the structure; most of that happens in the compile_tuple function though, so it should be easy to modify it to do what you want.
What you'd have to adapt:
change name for number (and change the pattern accordingly to lpeg.R('09')^1, without the / '\0')
change the compile_tuple function to a build_table function (local function build_tanle(...) return {...} end should do the trick)
Try it out and see if something else needs to be changed; I might have missed something.
You can read the lpeg manual here if you're curious about how this stuff works.
Related
I'm reviewing some toy examples from Lua and I found the following one over there with respect to environments:
M = {} -- the module
complex = {} -- global complex numbers registry
mt = {} --metatable for complex numbers
function new (r, i)
local cp = {}
cp = {r=r, i=i}
return setmetatable(cp,mt)
end
M.new = new -- add 'new' to the module
function M.op (...)
--Why does not it work?
local _ENV = complex
return ...
end
function M.add (c1, c2)
return new(c1.r + c2.r, c1.i + c2.i)
end
function M.tostring (c)
return string.format("(%g,%g)", c.r, c.i) --to avoid +-
end
mt.__tostring = M.tostring
mt.__add = M.add
complex.a = M.new(4,3)
complex.b = N.new(6,2)
--nil
M.op(a+b)
--It works
M,op(complex.a+complex.b)
The use of _ENV has no effect. However, if I use complex = _G, both lines work. How do set a local environment for M.op. I'm not asking for specific libraries, I just want to know why it does not work and how to fix it.
M.op(a+b)
This line doesn't do what you expect, because it uses values of a and b that are available when this method is called. It doesn't matter that you set _ENV value inside the method, as by the time the control gets there, the values referenced by a and b have already been retrieved and since both values are nil in your code, you probably get "attempt to perform arithmetic on global..." error.
how to fix it.
I'm not sure what exactly you want to fix, as you already reference the example that works. If you assign complex.a you can't assume that a will have the same value without mapping complex table to _ENV.
I have a file database. Inside that file I have something like:
DB_A = ...
DB_B = ...
.
.
.
DB_N = ...
I would like to parse the data and group them in lua code like this:
data={}
-- the result after parsing a file
data={
["DB_A"] = {...},
["DB_B"] = {...},
.
.
.
["DB_N"] = {...}
}
In other words, is it possible to create a table inside a table dynamically and assign the key to each table without previously knowing what will be the names of the key (that is something I can figure out after parsing the data from a database).
(Just as a note, I am using Lua 5.3.5; also, I apologize that my code resembles C more than Lua!)
Iterating through your input file line-by-line--which can be done with the Lua FILE*'s lines method--you can use string.match to grab the information you are looking for from each line.
#!/usr/bin/lua
local PATTERN = "(%S+)%s?=%s?(%S+)"
local function eprintf(fmt, ...)
io.stderr:write(string.format(fmt, ...))
return
end
local function printf(fmt, ...)
io.stdout:write(string.format(fmt, ...))
return
end
local function make_table_from_file(filename)
local input = assert(io.open(filename, "r"))
local data = {}
for line in input:lines() do
local key, value = string.match(line, PATTERN)
data[key] = value
end
return data
end
local function main(argc, argv)
if (argc < 1) then
eprintf("Filename expected from command line\n")
os.exit(1)
end
local data = make_table_from_file(argv[1])
for k, v in pairs(data) do
printf("data[%s] = %s\n", k, data[k])
end
return 0
end
main(#arg, arg)
The variable declared at the top of the file, PATTERN, is your capture pattern to be used by string.match. If you are unfamiliar with how Lua's pattern matching works, this pattern looks for a series of non-space characters with zero or one spaces to its right, an equal sign, another space, and then another series of non-space characters. The two series of non-space characters are the two matches--key and value--returned by string.match in the function make_table_from_file.
The functions eprintf and printf are my Lua versions of C-style formatted output functions. The former writes to standard error, io.stderr in Lua; and the latter writes to standard output, io.stdout in Lua.
In your question, you give a sample of what your expected output is. Within your table data, you want it to contain keys that correspond to tables as values. Based on the sample input text you provided, I assume the data contained within these tables are whatever comes to the right of the equal signs in the input file--which you represent with .... As I do not know what exactly those ...s represent, I cannot give you a solid example for how to separate that right-hand data into a table. Depending on what you are looking to do, you could take the second variable returned by string.match, which I called value, and further separate it using Lua's string pattern matching. It could look something like this:
...
local function make_table_from_value(val)
// Split `val` into distinct elements to form a table with `some_pattern`
return {string.match(val, some_pattern)}
end
local function make_table_from_file(filename)
local input = assert(io.open(filename, "r"))
local data = {}
for line in input:lines() do
local key, value = string.match(line, PATTERN)
data[key] = make_table_from_value(value)
end
return data
end
...
In make_table_from_value, string.match will return some number of elements, based on whatever string pattern you provide as its second argument, which you can then use to create a table by enclosing the function call in curly braces. It will be a table that uses numerical indices as keys--rather than strings or some other data type--starting from 1.
I want to know how to get the table hex id. I know that doing:
local some_var = {}
print (some_var)
the result is (for instance):
table: 0x21581c0
I want the hex without the table: string. I know that maybe some of you suggest me to make a regular expression (or something similar) to remove those chars, but I want to avoid that, and just get the 0x21581c0
Thanks
This is simpler and works for all types that are associated with pointers:
local function getId(t)
return string.format("%p", t)
end
print("string:", getId("hi"))
print("table:", getId({}))
print("userdata:", getId(io.stdin))
print("function:", getId(print))
print("number:", getId(1))
print("boolean:", getId(false))
print("nil:", getId(nil))
Result:
string: 0x0109f04638
table: 0x0109f0a270
userdata: 0x01098076c8
function: 0x0109806018
number: NULL
boolean: NULL
nil: NULL
In the standard implementation, there is the global 'print' variable that refers to a standard function that calls, through the global variable 'tostring', a standard function described here. The stanard 'tostring' function is the only way to retrieve the hexadecimal number it shows for a table.
Unfortunately, there is no configuration for either of the functions to do anything differently for all tables.
Nonetheless, there are several points for modification. You can create you own function and call that every time instead, or point either of the the global variables print or tostring to you own functions. Or, set a __tostring metamethod on each table you need tostring to return a different answer for. The advantage to this is it gets you the format you want with only one setup step. The disadvantage is that you have to set up each table.
local function simplifyTableToString(t)
local answer = tostring(t):gsub("table: ", "", 1)
local mt = getmetatable(t)
if not mt then
mt = {}
setmetatable(t, mt)
end
mt.__tostring = function() return answer end
end
local a = {}
local b = {}
print(a, b)
simplifyTableToString(a)
print(a, b)
Without complex patterns, you can just search for the first space, and grab the substring of what follows.
function get_mem_addr (object)
local str = tostring(object)
return str:sub(str:find(' ') + 1)
end
print(get_mem_addr({})) -- 0x109638
print(get_mem_addr(function () end)) -- 0x108cf8
This function will work with tables and functions, but expect errors if you pass it anything else.
Or you can use a little type checking:
function get_mem_addr (o)
return tostring(o):sub(type(o):len() + 3)
end
The table id stated by the OP is invalid in the version of Lua I am using (5.1 in Roblox). A valid ID is length 8, not 9 as in your example. Either way, just use string.sub to get the sub-string you are after.
string.sub(tostring({}), 8)
The reason is, 'table: ' is 7 characters long, so we take from index 8 through the end of the string which returns the hex value.
I need this for a game server using Lua..
I would like to be able to save all combinations of a name
into a string that can then be used with:
if exists (string)
example:
ABC_-123
aBC_-123
AbC_-123
ABc_-123
abC_-123
etc
in the game only numbers, letters and _ - . can be used as names.
(A_B-C, A-B.C, AB_8 ... etc)
I understand the logic I just don't know how to code it:D
0-Lower
1-Upper
then
000
001
etc
You can use recursive generator. The first parameter contains left part of the string generated so far, and the second parameter is the remaining right part of the original string.
function combinations(s1, s2)
if s2:len() > 0 then
local c = s2:sub(1, 1)
local l = c:lower()
local u = c:upper()
if l == u then
combinations(s1 .. c, s2:sub(2))
else
combinations(s1 .. l, s2:sub(2))
combinations(s1 .. u, s2:sub(2))
end
else
print(s1)
end
end
So the function is called in this way.
combinations("", "ABC_-123")
You only have to store intermediate results instead of printing them.
If you are interested only in the exists function then you don't need all combinations.
local stored_string = "ABC_-123"
function exists(tested_string)
return stored_string:lower() == tested_string:lower()
end
You simply compare the stored string and the tested string in case-insensitive way.
It can be easily tested:
assert(exists("abC_-123"))
assert(not exists("abd_-123"))
How to do this?
There's native function in Lua to generate all permutations of a string, but here are a few things that may prove useful.
Substrings
Probably the simplest solution, but also the least flexible. Rather than combinations, you can check if a substring exists within a given string.
if str:find(substr) then
--code
end
If this solves your problem, I highly reccomend it.
Get all permutations
A more expensive, but still a working solution. This accomplishes nearly exactly what you asked.
function GetScrambles(str, tab2)
local tab = {}
for i = 1,#str do
table.insert(tab, str:sub(i, i))
end
local tab2 = tab2 or {}
local scrambles = {}
for i = 0, Count(tab)-1 do
local permutation = ""
local a = Count(tab)
for j = 1, #tab do
tab2[j] = tab[j]
end
for j = #tab, 1, -1 do
a = a / j
b = math.floor((i/a)%j) + 1
permutation = permutation .. tab2[b]
tab2[b] = tab2[j]
end
table.insert(scrambles, permutation)
end
return scrambles
end
What you asked
Basically this would be exactly what you originally asked for. It's the same as the above code, except with every substring of the string.
function GetAllSubstrings(str)
local substrings = {}
for i = 1,#str do
for ii = i,#str do
substrings[#substrings+1]=str:sub(ii)
end
end
return substrings
end
Capitals
You'd basically have to, with every permutation, make every possible combination of capitals with it.
This shouldn't be too difficult, I'm sure you can code it :)
Are you joking?
After this you should probably be wondering. Is all of this really necessary? It seems like a bit much!
The answer to this lies in what you are doing. Do you really need all the combinations of the given characters? I don't think so. You say you need it for case insensitivity in the comments... But did you know you could simply convert it into lower/upper case? It's very simple
local str = "hELlO"
print(str:lower())
print(str:upper())
This is HOW you should store names, otherwise you should leave it case sensitive.
You decide
Now YOU pick what you're going to do. Whichever direction you pick, I wish you the best of luck!
I have a search replace script which works to replace strings. It already has options to do case insensitive searches and "escaped" matches (eg allows searching for % ( etc in the search.
How ever I have now been asked to match whole words only, I have tried adding %s to each end, but that does not match words at the end of a string and I can't then work out how to trap for the white-space items found to leave them intact during the replace.
Do I need to redo the script using string.find and add logic for the word checking or this possible with patterns.
The two functions I use for case insensitive and escaped items are as follows both return the pattern to search for.
-- Build Pattern from String for case insensitive search
function nocase (s)
s = string.gsub(s, "%a", function (c)
return string.format("[%s%s]", string.lower(c),
string.upper(c))
end)
return s
end
function strPlainText(strText)
-- Prefix every non-alphanumeric character (%W) with a % escape character, where %% is the % escape, and %1 is original character
return strText:gsub("(%W)","%%%1")
end
I have a way of doing what I want now, but it's inelegant. Is there a better way?
local strToString = ''
local strSearchFor = strSearchi
local strReplaceWith = strReplace
bSkip = false
if fhGetDataClass(ptr) == 'longtext' then
strBoxType = 'm'
end
if pWhole == 1 then
strSearchFor = '(%s+)('..strSearchi..')(%s+)'
strReplaceWith = '%1'..strReplace..'%3'
end
local strToString = string.gsub(strFromString,strSearchFor,strReplaceWith)
if pWhole == 1 then
-- Special Case search for last word and first word
local strSearchFor3 = '(%s+)('..strSearchi..')$'
local strReplaceWith3 = '%1'..strReplace
strToString = string.gsub(strToString,strSearchFor3,strReplaceWith3)
local strSearchFor3 = '^('..strSearchi..')(%s+)'
local strReplaceWith3 = strReplace..'%2'
strToString = string.gsub(strToString,strSearchFor3,strReplaceWith3)
end
have a way of doing what I want now, but it's inelegant. Is there a better way?
There is an undocumented feature of Lua's pattern matching library called the Frontier Pattern, which will let you write something like this:
function replacetext(source, find, replace, wholeword)
if wholeword then
find = '%f[%a]'..find..'%f[%A]'
end
return (source:gsub(find,replace))
end
local source = 'test testing this test of testicular footest testimation test'
local find = 'test'
local replace = 'XXX'
print(replacetext(source, find, replace, false)) --> XXX XXXing this XXX of XXXicular fooXXX XXXimation XXX
print(replacetext(source, find, replace, true )) --> XXX testing this XXX of testicular footest testimation XXX
do you mean if you pass nocase() foo, you want [fooFOO] instead of [fF][oO][oO]? if so, you could try this?
function nocase (s)
s = string.gsub(s, "(%a+)", function (c)
return string.format("[%s%s]", string.lower(c),
string.upper(c))
end)
return s
end
and if you want an easy way to split a sentence into words, you can use this:
function split(strText)
local words = {}
string.gsub(strText, "(%a+)", function(w)
table.insert(words, w)
end)
return words
end
once you've gotten the words split, it's pretty easy to iterate over the words in the table and do a full comparison against each word.