Manual:Table Functions

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Revision as of 14:03, 7 April 2023 by Vadi (talk | contribs) (Make table.index_of easier to find)
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Table Functions

These functions are used to manipulate tables. Through them you can add to tables, remove values, check if a value is present in the table, check the size of a table, and more.

spairs

spairs(tbl, sortFunction)
Returns an iterator similar to pairs(tbl) but sorts the keys before iterating through them.
Parameters
  • tbl:
The table to iterate over
  • sortFunction:
The function to use for determining what order to iterate the items in the table. Defaults to alphanumeric sorting by key. Similar to table.sort. See example for more info.
Mudlet VersionAvailable in Mudlet4.10+
Example
local tbl = { Tom = 40, Mary = 50, Joe = 23 }

-- This iterates, sorting based on the key (which is the name in this case)
for name, thingies in spairs(tbl) do
  echo(string.format("%s has %d thingies\n", name, thingies))
end
--[[
Joe has 23 thingies
Mary has 50 thingies
Tom has 40 thingies
--]]

-- The function used below sorts based on the value. 
for name, thingies in spairs(tbl, function(t,a,b) return t[a] < t[b] end) do --iterate from lowest value to highest
  echo(string.format("%s has %d thingies\n", name, thingies))
end
--[[
Joe has 23 thingies
Tom has 40 thingies
Mary has 50 thingies
--]]

-- This function can be used to sort a group of Geyser gauges based on their value (what percentage of the gauge is filled)
local gaugeSort = function(t,a,b)
    local avalue = t[a].value or 100 -- treat non-gauges as though they are full gauges. If you know for -sure- the table only has gauges the 'or 100' is not needed.
    local bvalue = t[b].value or 100
    return avalue < bvalue
end
for _,gauge in spairs(tblOfGauges, gaugeSort) do
  -- do what you want with the gauges. First one will be the least full, then the next least full, until the last which will be the most full. 
  -- If you replace the < with a > it will go from most full to least full instead.
end

table.collect

table.collect(tbl, func)
Returns a table that is every key-value pair from tbl for which func(key,value) returns true
Parameters
  • tbl:
The table to collect items from
  • func:
the function to use for testing if an item should be collected or not
Mudlet VersionAvailable in Mudlet4.8+
Example
local vitals = { hp = 3482, maxhp = 5000, mana = 3785, maxmana = 5000 }
local pullHpKeys = function(key, value)
  if string.match(key, "hp") then return true end
end
local hp_values = table.collect(vitals, pullHpKeys)
display(hp_values)

This prints the following: 

{
  hp = 3482,
  maxhp = 5000
}
Returns
A table containing all the key/value pairs from tbl that cause func(key,value) to return true

table.complement

table.complement (set1, set2)
Returns a table that is the relative complement of the first table with respect to the second table. Returns a complement of key/value pairs.
Parameters
  • table1:
  • table2:
Example
local t1 = {key = 1,1,2,3}
local t2 = {key = 2,1,1,1}
local comp = table.complement(t1,t2)
display(comp)

This prints the following: 

  key = 1,
  [2] = 2,
  [3] = 3
Returns
A table containing all the key/value pairs from table1 that do not match the key/value pairs from table2.

table.concat

table.concat(table, delimiter, startingindex, endingindex)
Joins a table into a string. Each item must be something which can be transformed into a string.
Returns the joined string.
See also: string.split
Parameters
  • table:
The table to concatenate into a string. Passed as a table.
  • delimiter:
Optional string to use to separate each element in the joined string. Passed as a string.
  • startingindex:
Optional parameter to specify which index to begin the joining at. Passed as an integer.
  • endingindex:
Optional parameter to specify the last index to join. Passed as an integer.
Examples
--This shows a basic concat with none of the optional arguments
testTable = {1,2,"hi","blah",}
testString = table.concat(testTable)
--testString would be equal to "12hiblah"

--This example shows the concat using the optional delimiter
testString = table.concat(testTable, ", ")
--testString would be equal to "1, 2, hi, blah"

--This example shows the concat using the delimiter and the optional starting index
testString = table.concat(testTable, ", ", 2)
--testString would be equal to "2, hi, blah"

--And finally, one which uses all of the arguments
testString = table.concat(testTable, ", ", 2, 3)
--testString would be equal to "2, hi"

table.contains

table.contains (t, value)
Determines if a table contains a value as a key or as a value (recursive as of Mudlet 4.8+).
Returns true or false
See also
table.index_of

Note Note: This tests for the 'value' parameter as either a key or value in the table. That means this will return true: table.contains({"Bob"}, 1)

Parameters
  • t:
The table in which you are checking for the presence of the item as key or value..
  • value:
The value you are checking for within the table.
Example
local test_table = {"value1", "value2", "value3", "value4", "value5", "value6", "value7"}
if table.contains(test_table, "value1") then 
   print("Got value 1!")
else
   print("Don't have it. Sorry!")
end

-- if the table has just a few values, you can skip making a local, named table:
if table.contains({"Anna", "Alanna", "Hanna"}, "Anna") then 
   print("Have 'Anna' in the list!")
else
   print("Don't have the name. Sorry!")
end

-- don't forget, it will return true if the item is a key in the table as well
display(table.contains({"bob"}, 1) -- displays true, as 1 is the key/index for "bob"
-- If you really only want to check values, try table.index_of, which returns the key a value is found at, or nil if it is not found.

table.deepcopy

table.deepcopy (table)
Returns a complete copy of the table.
Parameters
  • table:
The table which you'd like to get a copy of.
Example
local test_table = { "value1", "value2", "value3", "value4" }

-- by just doing:
local newtable = test_table
-- you're linking newtable to test_table. Any change in test_table will be reflected in newtable.

-- however, by doing:
local newtable = table.deepcopy(test_table)
-- the two tables are completely separate now.

table.intersection

table.intersection (set1, set2)
Returns a table that is the relative intersection of the first table with respect to the second table. Returns a intersection of key/value pairs.
Parameters
  • table1:
  • table2:
Example
local t1 = {key = 1,1,2,3}
local t2 = {key = 1,1,1,1}
local intersect = table.intersection(t1,t2)
display(intersect)

This prints the following: 

  key = 1,
  1
Returns
A table containing all the key/value pairs from table1 that match the key/value pairs from table2.

table.insert

table.insert(table, [pos,] value)
Inserts element value at position pos in table, shifting up other elements to open space, if necessary. The default value for pos is n+1, where n is the length of the table, so that a call table.insert(t,x) inserts x at the end of table t.
See also: table.remove
Parameters
  • table:
The table in which you are inserting the value
  • pos:
Optional argument, determining where the value will be inserted.
  • value:
The variable that you are inserting into the table. Can be a regular variable, or even a table or function*.
Examples
--it will inserts what inside the variable of matches[2] into at the end of table of 'test_db_name'. 
table.insert(test_db_name, matches[2])
--it will inserts other thing at the first position of this table.
table.insert(test_db_name, 1, "jgcampbell300")

--[=[

This results:

test_db_name = {
    "jgcampbell300",
    "SlySven"
}
]=]

table.index_of

table.index_of(table, value)

Returns the index (location) of an item in an indexed table, or nil if it's not found. Think of it as a table.find function (although it is called table.index_of).

Parameters
  • table:
The table in which you are inserting the value
  • value:
The variable that you are searching for in the table.
Examples
-- will return 1, because 'hi' is the first item in the list
table.index_of({"hi", "bye", "greetings"}, "hi")

-- will return 3, because 'greetings' is third in the list
table.index_of({"hi", "bye", "greetings"}, "greetings")

-- you can also use this in combination with table.remove(), which requires the location of the item to delete
local words = {"hi", "bye", "greetings"}
table.remove(words, table.index_of(words, "greetings"))

-- however that won't work if the word isn't present, table.remove(mytable, nil (from table.index_of)) will give an error
-- so if you're unsure, confirm with table.contains first
local words = {"hi", "bye", "greetings"}
if table.contains(words, "greetings") then
  table.remove(words, table.index_of(words, "greetings"))
end

table.is_empty

table.is_empty(table)
Check if a table is devoid of any values.
Parameters
  • table:
The table you are checking for values.

table.keys

table.keys(table)
return a table that is the collection of the keys in use by the table passed in
Parameters
  • table:
The table you are collecting keys from.
Mudlet VersionAvailable in Mudlet4.1+
Example
   local testTable = {
     name = "thing",
     type = "test",
     malfunction = "major"
   }
   local keys = table.keys(testTable)
   -- key is now a table { "name", "type", "malfunction" } but the order cannot be guaranteed
   -- as pairs() does not iterate in a guaranteed order. If you want the keys in alphabetical
   -- run table.sort(keys) and keys == { "malfunction", "name", "type" }

table.load

table.load(location, table)
Load a table from an external file into mudlet.
See also: table.save

Tip: you can load a table from anywhere on your computer, but it's preferable to have them consolidated somewhere connected to Mudlet, such as the current profile.

Parameters
  • location:
Where you are loading the table from. Can be anywhere on your computer.
  • table:
The table that you are loading into - it must exist already.
Example:
-- This will load the table mytable from the lua file mytable present in your Mudlet Home Directory.
mytable = mytable or {}
if io.exists(getMudletHomeDir().."/mytable.lua") then
  table.load(getMudletHomeDir().."/mytable.lua", mytable) -- using / is OK on Windows too.
end

table.matches

table.matches(tbl, pattern, [pattern2], [pattern_n], [check_keys])
Returns a table of key-value pairs from tbl which match one of the supplied patterns when checked via string.match. This function is not recursive - nested tables within tbl will not be checked, only the top-level.
Parameters
  • tbl:
the table you want to check over using string.match
  • pattern:
the pattern you want to use to check each key-value pair. You may specify multiple patterns, separated by commas
  • check_keys:
boolean argument, set to true if you want to include a key-value pair if the key or value string.matches. If you do not set this, only the value will be checked
Mudlet VersionAvailable in Mudlet4.8+
Example
local items = { this = "that", hp = 400, [4] = "toast", something = "else", more = "keypairs" }
local matches = table.matches(items, "%d")
-- here matches will be { hp = 400 }
local matches = table.matches(items, "%d", "that", true)
-- here matches will be { hp = 400, this = "that", [4] = "toast" }

table.maxn

table.maxn(table)
Returns the largest positive numerical index of the given table, or zero if the table has no positive numerical indices. (To do its job this function does a linear traversal of the whole table.)

table.n_collect

table.n_collect(tbl, func(value))
returns a table which contains every unique value from tbl for which func(value) returns true. Ignores keys. Table returned is ipairs iterable.
Parameters
  • tbl:
the table you want to collect values from
  • func(value):
the function to check each value against
Mudlet VersionAvailable in Mudlet4.8+
Example
local items = { 
  this = "that",
  other = "thing",
  otter = "potato",
  honey = "bee"
}
local beginsWithTH = function(value)
  if string.match(value, "^th") then return true end
end
local nmatches = table.n_collect(items, beginsWithTH)
-- nmatches will be { "that", "thing" }
-- the order will not necessarily be preserved

table.n_filter

table.n_filter(table, function(element[, index[, table]]))
Returns a new table with all elements that pass the test implemented by the provided function. If no elements pass the test, an empty table will be returned.
Parameters
  • table: the table you wish to filter values out of.
  • function: the function to test each element of the array. Return true to keep the element, false otherwise. It accepts three arguments:
    • element: The current element being processed in the table.
    • index: (optional) The index of the current element being processed in the table.
    • table: (optional) The table n_filter was called upon.
Examples

Filter out small values: 

local function isBigEnough(value) return value >= 10 end
local filtered = table.n_filter({12, 5, 8, 130, 44}, isBigEnough)
-- filtered: {12, 130, 44}

Filter out invalid entries: 

local invalidEntries = 0
local entries = {
  { id = 15 }, { id = -1 }, { id = 0 }, { id = 3 },
  { id = 12.2 }, { }, { id = nil }, { id = false },
  { id = 'not a number' }
}

local function isNumber(t) return t and type(t) == 'number' end
local function filterByID(item)
  if isNumber(item.id) and item.id ~= 0 then
    return true
  end
  invalidEntries = invalidEntries + 1
  return false
end

local entriesByID = table.n_filter(entries, filterByID)
-- invalidEntries: 5
-- entriesByID: { { id = 15 }, { id = -1 }, { id = 3 }, { id = 12.2 } }

Filter out content based on search criteria: 

local fruits = {'apple', 'banana', 'grapes', 'mango', 'orange'}
local function filterItems(t, query)
  return table.n_filter(t, function(item)
    return item:lower():find(query:lower())
  end)
end
filterItems(fruits, 'ap') -- {'apple', 'grapes'}
filterItems(fruits, 'an') -- {'banana', 'mango', 'orange'}

table.n_flatten

table.n_flatten(table)
Returns a new table with the sub-table elements concatenated into it.
Parameters
  • table: A table of nested sub-tables you wish to flatten.
Example
local t1 = {1, 2, {3, 4}};
local t2 = {1, 2, {3, 4, {5, 6}}};
local t3 = {1, 2, {3, 4, {5, 6, {7, 8, {9, 10}}}}};
table.n_flatten(t1) -- {1, 2, 3, 4}
table.n_flatten(t2) -- {1, 2, 3, 4, 5, 6}
table.n_flatten(t3) -- {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

table.n_matches

table.n_matches(tbl, pattern, [pattern2], [patternN])
Returns a table of unique values within tbl which one of the supplied patterns matches using string.match
Parameters
  • tbl:
The table you want to search for values
  • pattern:
The pattern you want to check each value with, using string.match. You can supply multiple patterns, separated by commas
Mudlet VersionAvailable in Mudlet4.8+
Example
local items = { this = "that", [4] = "other", hp = 500, mana = 40 }
local matches = table.n_matches(items, "%a")
-- matches will be { "that", "other" }
-- order is not preserved/guaranteed

table.n_union

table.n_union (table1, table2)
Returns a numerically indexed table that is the union of the provided tables (that is - merges two indexed lists together). This is a union of unique values. The order and keys of the input tables are not preserved.
Parameters
  • table1: the first table as an indexed list.
  • table2: the second table as an indexed list.
Example
display(table.n_union({"bob", "mary"}, {"august", "justinian"}))

{
  "bob",
  "mary",
  "august",
  "justinian"
}

table.n_complement

table.n_complement (set1, set2)
Returns a table that is the relative complement of the first numerically indexed table with respect to the second numerically indexed table. Returns a numerically indexed complement of values.
Parameters
  • table1:
  • table2:
Example
local t1 = {1,2,3,4,5,6}
local t2 = {2,4,6}
local comp = table.n_complement(t1,t2)
display(comp)

This prints the following: 

  1,
  3,
  5
Returns
A table containing all the values from table1 that do not match the values from table2.

table.n_intersection

table.n_intersection (...)
Returns a numerically indexed table that is the intersection of the provided tables. This is an intersection of unique values. The order and keys of the input tables are not preserved
Example
local t1 = {1,2,3,4,5,6}
local t2 = {2,4,6}
local intersect = table.n_intersection(t1,t2)
display(intersect)

This prints the following: 

  2,
  4,
  6
Returns
A table containing the values that are found in every one of the tables.

table.pickle

table.pickle( t, file, tables, lookup )
Internal function used by table.save() for serializing data.

table.remove

table.remove(table, value_position)
Remove a value from an indexed table, by the values position in the table.
See also: table.insert
Parameters
  • table
The indexed table you are removing the value from.
  • value_position
The indexed number for the value you are removing.
Example
testTable = { "hi", "bye", "cry", "why" }
table.remove(testTable, 1) -- will remove hi from the table
-- new testTable after the remove
testTable = { "bye", "cry", "why" }
-- original position of hi was 1, after the remove, position 1 has become bye
-- any values under the removed value are moved up, 5 becomes 4, 4 becomes 3, etc

Note Note: To remove a value from a key-value table, it's best to simply change the value to nil. 

testTable = { test = "testing", go = "boom", frown = "glow" }
table.remove(testTable, test) -- this will error
testTable.test = nil -- won't error
testTable["test"] = nil -- won't error

table.save

table.save(location, table)
Save a table into an external file in location.
See also: table.load
Parameters
  • location:
Where you want the table file to be saved. Can be anywhere on your computer.
  • table:
The table that you are saving to the file.
Example:
-- Saves the table mytable to the lua file mytable in your Mudlet Home Directory
table.save(getMudletHomeDir().."/mytable.lua", mytable)

table.sort

table.sort(Table [, comp])
Sorts table elements in a given order, in-place, from Table[1] to Table[n], where n is the length of the table.
If comp is given, then it must be a function that receives two table elements, and returns true when the first is less than the second (so that not comp(a[i+1],a[i]) will be true after the sort). If comp is not given, then the standard Lua operator < is used instead.
The sort algorithm is not stable; that is, elements considered equal by the given order may have their relative positions changed by the sort.
See https://www.lua.org/pil/19.3.html for more info

table.size

table.size (t)
Returns the size of a key-value table (this function has to iterate through all of the table to count all elements).
Returns a number.
Parameters
  • t:
The table you are checking the size of.

Note Note: For index based tables you can get the size with the # operator: This is the standard Lua way of getting the size of index tables i.e. ipairs() type of tables with numerical indices. To get the size of tables that use user defined keys instead of automatic indices (pairs() type) you need to use the function table.size() referenced above. 

local test_table = { "value1", "value2", "value3", "value4" }
myTableSize = #test_table
-- This would return 4.
local myTable = { 1 = "hello", "key2" = "bye", "key3" = "time to go" }
table.size(myTable)
-- This would return 3.

table.unpickle

table.unpickle( t, tables, tcopy, pickled )
Internal function used by table.load() for deserialization.

table.update

table.update(table1, table2)
Returns a table in which key/value pairs from table2 are added to table1, and any keys present in both tables are assigned the value from table2, so that the resulting table is table1 updated with information from table2.
Example
display(table.update({a = 1, b = 2, c = 3}, {b = 4, d = 5}))
{
   a = 1,
   b = 4,
   c = 3,
   d = 5
}

-- to just set a table to new values, assign it directly:
mytable = {key1 = "newvalue"}

table.union

table.union(...)
Returns a table that is the union of the provided tables. This is a union of key/value pairs. If two or more tables contain different values associated with the same key, that key in the returned table will contain a subtable containing all relevant values. See table.n_union() for a union of values. Note that the resulting table may not be reliably traversable with ipairs() due to the fact that it preserves keys. If there is a gap in numerical indices, ipairs() will cease traversal.
Examples
tableA = {
   [1] = 123,
   [2] = 456,
   ["test"] = "test",
}
---
tableB = {
   [1] = 23,
   [3] = 7,
   ["test2"] = function() return true end,
}
---
tableC = {
   [5] = "c",
}
---
table.union(tableA, tableB, tableC)
-- will return the following:
{
   [1] = {
      123,
      23,
   },
   [2] = 456,
   [3] = 7,
   [5] = "c",
   ["test"] = "test",
   ["test2"] = function() return true end,
}
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