Server Side Programming Articles - Page 1018 of 2650

There’s no continue statement in Lua, and it’s not because the developers of the Lua programming language felt that it is of no use, in fact, in the official documentation they mentioned “continue was only one of a number of possible new control flow mechanisms”. This clearly shows that the developers of the Lua programming language aren’t a huge fan of the “continue” statement.If we need to break it down the fact that why Lua developers doesn’t wanted a “continue” statement, then it comes down to two possible answers, these are −They think that the “continue” statement is just another ... Read More

Yes, the arrays in Lua start with index 1 as the first index and not index 0 as you might have seen in most of the programming languages.ExampleConsider the example shown below − Live Demoarr = {10, 11, 12, 13, 14} print(arr[0]) print(arr[1])In the above example, we are printing the values at indices 0 and 1, and by default, the value at the 0 index will be nil, as in Lua, the arrays start indexing from 1, not 0.Outputnil 10So, now we know that the arrays are 1-index based not 0-index based. But, wait, why 1-index and 0-index?Actually, there have been ... Read More

In Lua, we make use of both the pairs() and ipairs() function when we want to iterate over a given table with the for loop. Both these functions return key-value pairs where the key is the index of the element and the value is the element stored at that index table.While both of them have some similarities, it is also good to know that they have some very notable differences that we should be aware of.The first difference between the pairs() and ipairs() function is that the pairs() function doesn’t maintain the key order whereas the ipairs() function surely does.ExampleConsider ... Read More

The ~= symbol or operator in Lua is known as the not-equal to operator. In many programming languages you might have seen the symbol != which is also known as the not equals operator.Let’s consider a few examples where we can make use of the not equals operator.ExampleConsider the examples shown below − Live Demoa = 2 b = 3 print(a ~= b)OutputtrueExample Live Demot1 = {4,2,3} t2 = {2,3,4} print(t1 ~= t2)Outputtrue

The unary operator # is known as the Length operator in Lua. It is used almost everywhere in Lua. By everywhere, I meant that anywhere we would require to calculate the length of the any string or can also be used in tables also, but when it comes to table, it is generally not preferred to use the # operator as it doesn’t calculate the number of elements present inside the table.Let’s explore different examples of the length operator to understand how we can make use of it.ExampleConsider the example shown below − Live Demoprint(#"abcdefg") print(#{"a", "b", "c", 77})Output7 4In the ... Read More

While we know that Lua does a great job when we want to use it as an embedded language, it can also exceed its basic uses and can be used in extreme cases such as Machine Learning and statistical analysis.There are many scientific libraries that are present in the market for this particular case of making more out of Lua. Let’s explore what these libraries are and what they do.The first name that comes to my mind when talking about Lua and machine learning in the same sentence is of the Torch project. The torch project is a scientific computing ... Read More

In Lua, any function is a closure. In a narrower sense, a closure is an anonymous function like the returned function in your example.Closures are first-class: they can be assigned to variables, passed to functions and returned from them. They can be both keys and values in Lua tables.Unlike C++ or PHP, closures in Lua have access to all variables in local scope— upvalues with no need to declare upvalues explicitly. Upvalues survive when code execution leaves the block where they were set.Now that we know what a closure is and why it is useful, let’s take an example and ... Read More

Whenever we try to access a field that hasn’t been declared in a table in Lua, the answer we get is nil. While this is true, but the reason for it is that when such access happens, the interpreter triggers a search for an __index metamethod and if it doesn’t find any method named __index, then we get nil as an answer; else we will get whatever the value of the field is set in the __index metamethod.We can explicitly put in the __index method in a table and provide it the named values that we want it to return ... Read More

When we want to return multiple values from a table, we make use of the table.unpack() function. It takes a list and returns multiple values.Syntaxtable.unpack{x, y, z, ....}ExampleThe table.unpack() function provides us with all the values that are passed to it as an argument, but we can also specify which value we want by following the example shown below − Live Demoa, b = table.unpack{1, 2, 3} print(a, b)In the above example, even though the table.unpack() function contains different values, namely 1, 2 and 3, we only are storing the first two values, i.e., a and b and the value 3 ... Read More

When we want to return a table as a result from multiple values passed into a function, then we make use of the table.pack() function. The table.pack() function is a variadic function.Syntaxtable.pack(x, y, z, ....)ExampleThe table.pack() function provides a table formed with all the values that are passed to it as an argument, consider the example shown below − Live Demoa = table.pack(1, 2, 3) print(a) print(a.n)In the above example, we passed three numbers to the table.pack() function as an argument and then we are printing the returned value, i.e., which will hold the address of the table that contains the ... Read More