In Lua, the function table.maxn is used to get the size of an array, but for a hash table, you can use another way. Here are the different methods to get the size of a hash in Lua:
### Method 1: Using the # operator
In Lua, the # operator returns the length of a table, which for a hash table, is the number of elements in the table. So, you can use the # operator to get the size of a hash table as follows:
-- create hash table
local hash = {a = 1, b = 2, c = 3}
-- get size of hash table
local size = #hash
-- print size of hash table
print(size) -- output: 0 (NOTE: this will output 0 because a hash table is not treated as an array in Lua)
### Method 2: Using the table.getn function
In Lua, the table.getn function returns the length of an array table, but this function can also be used to get the size of a hash table. However, note that table.getn has been deprecated since Lua 5.1, so it should not be used anymore.
-- create hash table
local hash = {a = 1, b = 2, c = 3}
-- get size of hash table
local size = table.getn(hash)
-- print size of hash table
print(size) -- output: 0
### Method 3: Using a loop to count the elements
Another way to get the size of a hash table in Lua is to loop through the table and count the elements. This method is not as efficient as the previous methods, but it works for a small hash table.
-- create hash table
local hash = {a = 1, b = 2, c = 3}
-- get size of hash table
local size = 0
for k, v in pairs(hash) do
size = size + 1
end
-- print size of hash table
print(size) -- output: 3
In general, it is not recommended to rely on the size of a hash table in Lua because the hash table can automatically resize itself as needed.