Usually a simple hash function works by taking the “component parts” of the input (characters in the case of a string), and multiplying them by the powers of some constant, and adding them together in some integer type. So for example a typical (although not especially good) hash of a string might be: (first char) … Read more
Concurrent programming regards operations that appear to overlap and is primarily concerned with the complexity that arises due to non-deterministic control flow. The quantitative costs associated with concurrent programs are typically both throughput and latency. Concurrent programs are often IO bound but not always, e.g. concurrent garbage collectors are entirely on-CPU. The pedagogical example of … Read more
Enter this code in your address bar (in your browser) and press enter. Then you can edit all the content of the webpage! javascript:document.body.contentEditable=”true”; document.designMode=”on”; void 0 That is the coolest “one-liner” I know =)
Because HTTP is stateless, in order to associate a request to any other request, you need a way to store user data between HTTP requests. Cookies or URL parameters ( for ex. like http://example.com/myPage?asd=lol&boo=no ) are both suitable ways to transport data between 2 or more request. However they are not good in case you … Read more
Eli, the code you’ve settled on is incorrect. A point near the line on which the segment lies but far off one end of the segment would be incorrectly judged near the segment. Update: The incorrect answer mentioned is no longer the accepted one. Here’s some correct code, in C++. It presumes a class 2D-vector … Read more
Expression: Something which evaluates to a value. Example: 1+2/x Statement: A line of code which does something. Example: GOTO 100 In the earliest general-purpose programming languages, like FORTRAN, the distinction was crystal-clear. In FORTRAN, a statement was one unit of execution, a thing that you did. The only reason it wasn’t called a “line” was … Read more
The difference between compile time and run time is an example of what pointy-headed theorists call the phase distinction. It is one of the hardest concepts to learn, especially for people without much background in programming languages. To approach this problem, I find it helpful to ask What invariants does the program satisfy? What can … Read more
Currying is converting a single function of n arguments into n functions with a single argument each. Given the following function: function f(x,y,z) { z(x(y));} When curried, becomes: function f(x) { lambda(y) { lambda(z) { z(x(y)); } } } In order to get the full application of f(x,y,z), you need to do this: f(x)(y)(z); Many … Read more
A magic number is a direct usage of a number in the code. For example, if you have (in Java): public class Foo { public void setPassword(String password) { // don’t do this if (password.length() > 7) { throw new InvalidArgumentException(“password”); } } } This should be refactored to: public class Foo { public static … Read more
While each generated GUID is not guaranteed to be unique, the total number of unique keys (2128 or 3.4×1038) is so large that the probability of the same number being generated twice is very small. For example, consider the observable universe, which contains about 5×1022 stars; every star could then have 6.8×1015 universally unique GUIDs. … Read more