How to skip the first n item(s) of an iterator in Rust?
Turns out the .skip() method can be used, eg: use std::env; fn main() { for arg in env::args().skip(1) { println!(“Argument: {}”, arg); } }
iterator
Cannot use .begin() or .end() on an array
Arrays have no member functions as they aren’t a class type. This is what the error is saying. You can use std::begin(arr) and std::end(arr) from the <iterator> header instead. This also works with types that do have .begin() and .end() members, via overloading: #include <array> #include <vector> #include <iterator> int main() { int c_array[5] = … Read more
Some help understanding “yield”
A method using yield return must be declared as returning one of the following two interfaces: IEnumerable<SomethingAppropriate> IEnumerator<SomethingApropriate> (thanks Jon and Marc for pointing out IEnumerator) Example: public IEnumerable<AClass> YourMethod() { foreach (XElement header in headersXml.Root.Elements()) { yield return (ParseHeader(header)); } } yield is a lazy producer of data, only producing another item after the … Read more
Can/Should I inherit from an STL iterator?
Short answer Many consider that the class std::iterator does not offer much compared to regular type aliases, and even obfuscates them a bit by not explicitly providing the names and relying on the order of the template parameters instead. It is deprecated in C++17 and is likely to be gone in a few years. This … Read more
Find maximum value of a cv::Mat
You should use the OpenCV built-in function minMaxLoc instead of std function. Mat m; //Initialize m double minVal; double maxVal; Point minLoc; Point maxLoc; minMaxLoc( m, &minVal, &maxVal, &minLoc, &maxLoc ); cout << “min val: ” << minVal << endl; cout << “max val: ” << maxVal << endl;
Does std::map::iterator return a copy of value or a value itself?
I want to add a follow up answer to this question for people using C++11 iterators… The following code: std::map<std::string, std::string> m({{“a”,”b”},{“c”,”d”}}); for (auto i : m) { std::cout << i.first << “: ” << i.second << std::endl; } does copy the key and value since “auto” is a value by default, not a const … Read more
Pythonic way to iterate over bits of integer
There’s a trick for just getting the 1’s out of the binary representation without having to iterate over all the intervening 0’s: def bits(n): while n: b = n & (~n+1) yield b n ^= b >>> for b in bits(109): print(b) 1 4 8 32 64
what’s the point of having both Iterator.forEachRemaining() and Iterable.forEach()?
To understand why the two methods both exist, you need to first understand what are Iterator and Iterable. An Iterator basically is something that has a “next element” and usually, an end. An Iterable is something that contains elements in a finite or infinite sequence and hence, can be iterated over by keep getting the … Read more
What is the difference between an Iterator and a Generator?
An iterator traverses a collection one at a time. A generator generates a sequence, one item at a time. You might for example, iterate over the result of a generator…
Is end() required to be constant in an STL map/set?
You write (emphasis by me): ยง23.1.2.8 in the standard states that insertion/deletion operations on a set/map will not invalidate any iterators to those objects (except iterators pointing to a deleted element). Actually, the text of 23.1.2/8 is a bit different (again, emphasis by me): The insert members shall not affect the validity of iterators and … Read more