Theres a few ways you can do this. You can either add a background to the canvas you are currently working on, which if the canvas isn’t going to be redrawn every loop is fine. Otherwise you can make a second canvas underneath your main canvas and draw the background to it. The final way … Read more
EDIT (much later than original answer): MarkCC of Good Math, Bad Math recently wrote up an excellent discussion of the Halting problem with concrete examples. The halting problem is basically a formal way of asking if you can tell whether or not an arbitrary program will eventually halt. In other words, can you write a … Read more
Two’s complement is a clever way of storing integers so that common math problems are very simple to implement. To understand, you have to think of the numbers in binary. It basically says, for zero, use all 0’s. for positive integers, start counting up, with a maximum of 2(number of bits – 1)-1. for negative … Read more
The Internet itself pre-dates 1980, but the World Wide Web (“distributed hypertext via simple mechanisms”) as proposed and implemented by Tim Berners-Lee started in 1989/90. While the idea of hypertext had existed before (Nelson’s Xanadu had tried to implement a distributed scheme), the WWW was a new approach for implementing a distributed hypertext system. Berners-Lee … Read more
I am not a Matlab user so take that in mind. The main problem behind this is first to detect overflow/underflows That is sometimes hard because they appear also in other cases when the computation does not return zero or inf. For example during numerical integration overflow/underflows can cause the result to be wrong but … Read more
x86 is a CISC register machine, where at most 1 operand for any instruction can be an explicit memory address instead of a register, using an addressing mode like [rdi + rax*4]. (There are instruction which can have 2 memory operands with one or both being implicit, though: What x86 instructions take two (or more) … Read more
Generally it means that by increasing the level of abstraction one can make the problem easier to understand/resolve. Be careful with your abstractions though, the full quote at least as I heard it is, “You can solve every problem with another level of indirection, except for the problem of too many levels of indirection”.
Firmware developer here. This is a standard problem in embedded programming, and one that trips up many (even very experienced) developers. My assumption is that you are attempting to access a hardware register, and that register value can change over time (be it interrupt status, timer, GPIO indications, etc.). The volatile keyword is only part … Read more
Watch this lecture. The idea is that your program is a combination of a datatype and operations over it. The problem asks for an implementation that allows to add new cases of the type and new operations without the need for recompilation of the old modules and keeping static type safety(no casts or runtime type … 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