Closures, lambdas, and anonymous functions are not necessarily the same thing. An anonymous function is any function that doesn’t have (or, at least, need) its own name. A closure is a function that can access variables that were in its lexical scope when it was declared, even after they have fallen out of scope. Anonymous … Read more
Tries, also known as prefix-trees or crit-bit trees, have existed for over 40 years but are still relatively unknown. A very cool use of tries is described in “TRASH – A dynamic LC-trie and hash data structure“, which combines a trie with a hash function.
A lambda (or closure) encapsulates both the function pointer and variables. This is why, in C#, you can do: int lessThan = 100; Func<int, bool> lessThanTest = delegate(int i) { return i < lessThan; }; I used an anonymous delegate there as a closure (it’s syntax is a little clearer and closer to C than … Read more
Code coverage is a measurement of how many lines/blocks/arcs of your code are executed while the automated tests are running. Code coverage is collected by using a specialized tool to instrument the binaries to add tracing calls and run a full set of automated tests against the instrumented product. A good tool will give you … Read more
Usually for this type of question, if the regex is not simple enough to be derived directly, you can start from drawing a DFA and derive a regex from there. You should be able to derive the following DFA. q1, q2, q3, q4 are end states, with q1 also being the start state. q5 is … Read more
Given an arbitrary function, f, we define a function f’ which returns 1 on input n if f halts on input n. Now, for some number x we define a function g which, on input n, returns 1 if n = x, and otherwise calls f'(n). If functional equivalence were decidable, then deciding whether g … Read more
From http://www.sorting-algorithms.com/insertion-sort: Although it is one of the elementary sorting algorithms with O(n2) worst-case time, insertion sort is the algorithm of choice either when the data is nearly sorted (because it is adaptive) or when the problem size is small (because it has low overhead). For these reasons, and because it is also stable, insertion … Read more
I assume entropy was mentioned in the context of building decision trees. To illustrate, imagine the task of learning to classify first-names into male/female groups. That is given a list of names each labeled with either m or f, we want to learn a model that fits the data and can be used to predict … 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
A Y-combinator is a “functional” (a function that operates on other functions) that enables recursion, when you can’t refer to the function from within itself. In computer-science theory, it generalizes recursion, abstracting its implementation, and thereby separating it from the actual work of the function in question. The benefit of not needing a compile-time name … Read more