A predicate (‘PRED-i-cat’) is the part of a sentence that contains the verb and tells you something about the subject. For instance, in the sentence “Mike is eating”, we have the subject, ‘Mike’, and the predicate, ‘is eating’. In the context of computer science, we aren’t interested in stating a fact, but rather, in testing … Read more
A fixed point number has a specific number of bits (or digits) reserved for the integer part (the part to the left of the decimal point) and a specific number of bits reserved for the fractional part (the part to the right of the decimal point). No matter how large or small your number is, … Read more
You can only access elements by their primary key in a hashtable. This is faster than with a tree algorithm (O(1) instead of log(n)), but you cannot select ranges (everything in between x and y). Tree algorithms support this in Log(n) whereas hash indexes can result in a full table scan O(n). Also the constant … Read more
Yes, this is standard practice in academic literature. To understand it, it helps to know that the notion of “type” was invented in the 1930s, in the context of lambda calculus (in fact, even earlier, in the context of set theory). Since then, a whole branch of computational logic has emerged that is known as … Read more
Many algorithms will specify that duplicates are excluded. For example, the example algorithms in the MIT Algorithms book usually present examples without duplicates. It is fairly trivial to implement duplicates (either as a list at the node, or in one particular direction.) Most (that I’ve seen) specify left children as <= and right children as … 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
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
Different. foreach iterates over a list and performs some operation with side effects to each list member (such as saving each one to the database for example) map iterates over a list, transforms each member of that list, and returns another list of the same size with the transformed members (such as converting a list … Read more
P stands for polynomial time. NP stands for non-deterministic polynomial time. Definitions: Polynomial time means that the complexity of the algorithm is O(n^k), where n is the size of your data (e. g. number of elements in a list to be sorted), and k is a constant. Complexity is time measured in the number of … Read more
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