Module util.table
Useful operations on tables.
For arbitrary tables, we'll use the letter t.
For list-like tables, however, we'll use the letter l.
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TableUtils:filter (l, f)
-
Filter values of a list.
Parameters:
- l
table
- f
function
filter
Returns:
table
list containing only pairs (i, v) for which f(v) is true.
Usage:
local TableUtils = require "util.table"
local l = {1, 2, 3, 4, 5, 6}
local function f (v) return v % 2 == 0 end
local fl = TableUtils:filter(l, f)
print(table.concat(fl, ', '))
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TableUtils:map (l, m)
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Map values of a list.
Parameters:
- l
table
- m
function
mapping
Returns:
table
list containing only pairs (i, m(v)) for all (i, v) in l.
Usage:
local TableUtils = require "util.table"
local l = {1, 2, 3, 4, 5, 6}
local function m (v) return v * 2 end
local ml = TableUtils:map(l, m)
print(table.concat(ml, ', '))
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TableUtils:foldl (f, z, l)
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Perform a left fold of a list with a combining function and an initial value.
Parameters:
- f
function
combining function
- z
initial value
- l
table
list
Returns:
final state of the accumulator
Usage:
local TableUtils = require "util.table"
local l = {'a', 'b', 'c'}
print(TableUtils:foldl(string.concat, '', l))
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TableUtils:reverse (l)
-
Reverse a list.
Parameters:
Returns:
table
a list with all values of l in reverse order
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TableUtils:histogram (l)
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Create histogram of values of a list.
Parameters:
Returns:
table
histogram of values of l
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TableUtils:sum (t)
-
Sum all values of a table.
Parameters:
Returns:
number
sum of all values of t
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TableUtils:numOfPairs (t)
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Get the number of key-value pairs in a table.
Parameters:
Returns:
number
number of key-value pairs in t
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TableUtils:podium (t)
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Create a podium for a table of comparable values.
Parameters:
Returns:
-
the maximum value in
t, or nil if t is empty
-
number
the number of keys paired with the maximum value
-
table
the set of keys paired with the maximum value
Usage:
local TableUtils = require "util.table"
local t = {a=5, b=7, c=3, d=7, e=1}
local maxValue, tiedCount, tiedKeys = TableUtils:podium(t)
print(maxValue) print(tiedCount) print(table.concat(TableUtils:sortedKeys(tiedCount), ', '))
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TableUtils:sortedKeys (t)
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Create an ordered list with all the keys of a table.
Orders keys by
< on the key types, and then by < on the keys.
Parameters:
Returns:
table
an ordered list of all the keys of t
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TableUtils:sample (l)
-
Choose a random value from a list.
Parameters:
Returns:
-
some
l[i] such that i is in [1, #l], or nil if #l < 1
-
optional number
i, iff #l >= 1
See also:
-
TableUtils:uniqueSamples (l, m)
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Sample
m values from a list (without replacement).
Asserts that m is less than or equal to the length of the list.
Parameters:
Returns:
table
a list containing m unique samples from l
See also:
-
TableUtils:shuffleInPlace (l)
-
Shuffle the values of a list in-place.
Parameters:
See also:
-
TableUtils:sortedIter (t, f)
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Iterate through the pairs of a table, ordered by the keys.
Calls
f for all key-value pairs and checks if the return value is true.
If f(k, v) ever returns some ret different from nil and false,
then the iteration stops and ret is returned.
Parameters:
Returns:
the first true return value of f(k, v) or nil
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TableUtils:ipairsReversed (l)
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Iterate through all index-value pairs of a list, in reverse order.
Parameters:
Returns:
-
function
iterator
-
table
list
-
number
index
Usage:
local TableUtils = require "util.table"
local l = {'a', 'b', 'c'}
for i, v in TableUtils:ipairsReversed(l) do
print(i, v) end
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TableUtils:deepEqual (ta, tb[, checkmetatable=false])
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Recursively check if two tables are equal.
You can also check for metatable equality with
checkmetatable.
Parameters:
- ta
table
- tb
table
- checkmetatable
boolean
(default false)
Returns:
-
boolean
whether
ta and tb are equal
-
optional string
an error message (if
ta and tb are not equal)
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TableUtils:deepClone (t)
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Recursively clone a table. Also sets metatables.
Parameters:
Returns:
table
a clone of t