The term “referential transparency” comes from analytical philosophy, the branch of philosophy that analyzes natural language constructs, statements and arguments based on the methods of logic and mathematics. In other words, it is the closest subject outside computer science to what we call programming language semantics. The philosopher Willard Quine was responsible for initiating the … Read more
Type safety means that the compiler will validate types while compiling, and throw an error if you try to assign the wrong type to a variable. Some simple examples: // Fails, Trying to put an integer in a string String one = 1; // Also fails. int foo = “bar”; This also applies to method … Read more
I assume that you are looking for intuitive definitions, since the technical definitions require quite some time to understand. First of all, let’s remember a preliminary needed concept to understand those definitions. Decision problem: A problem with a yes or no answer. Now, let us define those complexity classes. P P is a complexity class … Read more
There are a number of good explanations of recursion in this thread, this answer is about why you shouldn’t use it in most languages.* In the majority of major imperative language implementations (i.e. every major implementation of C, C++, Basic, Python, Ruby,Java, and C#) iteration is vastly preferable to recursion. To see why, walk through … Read more
OK, I will describe first the simplest solution which is O(N^2), where N is the size of the collection. There also exists a O(N log N) solution, which I will describe also. Look here for it at the section Efficient algorithms. I will assume the indices of the array are from 0 to N – … Read more
First let’s understand what big O, big Theta and big Omega are. They are all sets of functions. Big O is giving upper asymptotic bound, while big Omega is giving a lower bound. Big Theta gives both. Everything that is Ө(f(n)) is also O(f(n)), but not the other way around. T(n) is said to be … Read more
Variable scope When you declare a local variable, that variable has a scope. Generally, local variables exist only within the block or function in which you declare them. function() { var a = 1; console.log(a); // works } console.log(a); // fails If I try to access a local variable, most languages will look for it … Read more
Lambda comes from the Lambda Calculus and refers to anonymous functions in programming. Why is this cool? It allows you to write quick throw away functions without naming them. It also provides a nice way to write closures. With that power you can do things like this. Python def adder(x): return lambda y: x + … Read more
Statically typed languages A language is statically typed if the type of a variable is known at compile time. For some languages this means that you as the programmer must specify what type each variable is; other languages (e.g.: Java, C, C++) offer some form of type inference, the capability of the type system to … Read more
Usually, I replace a recursive algorithm by an iterative algorithm by pushing the parameters that would normally be passed to the recursive function onto a stack. In fact, you are replacing the program stack by one of your own. var stack = []; stack.push(firstObject); // while not empty while (stack.length) { // Pop off end … Read more