Because you’re explicitly passing an initial size, which calls a constructor that has another parameter whose default value is s(). Just leave out the (0) (i.e. std::vector<s> v;) and it won’t happen. For completeness, the Standard 23.2.4-2 defines the constructor you’re calling as: explicit vector(size_type n, const T& value =T(), const Allocator& = Allocator()); Aside … Read more
It seems what you need is “slice patterns”: fn main() { let line = “127.0.0.1 1000 what!?”; let v = line.split_whitespace().take(3).collect::<Vec<&str>>(); if let [ip, port, msg] = &v[..] { println!(“{}:{} says ‘{}'”, ip, port, msg); } } Playground link Note the if let instead of plain let. Slice patterns are refutable, so we need to … Read more
The problem you’re having is that the compiler doesn’t know which versions of your template to instantiate. When you move the implementation of your function to x.cpp it is in a different translation unit from main.cpp, and main.cpp can’t link to a particular instantiation because it doesn’t exist in that context. This is a well-known … Read more
First, I’ll show you a recursive version. typedef std::vector<int> Vi; typedef std::vector<Vi> Vvi; // recursive algorithm to to produce cart. prod. // At any given moment, “me” points to some Vi in the middle of the // input data set. // for int i in *me: // add i to current result // recurse on … Read more
Mathematically speaking, the zero vector cannot be normalized. Its length will always remain 0. For given vector v = (v1, v2, …, vn) we have: ||v|| = sqrt(v1^2 + v2^2 + … + vn^2). Let us remember that a normalized vector is one that has ||v||=1. So for v = 0 we have: ||0|| = … Read more
There is no such helper method on the Iterator trait directly. However, there are two main ways to do it: Use the [T]::chunks() method (which can be called on a Vec<T> directly). However, it has a minor difference: it won’t produce None, but the last iteration yields a smaller slice. For always-exact slices that omit … Read more
Since C++20, there are freestanding std::erase and std::erase_if functions that work on containers and simplify things considerably: std::erase(myNumbers, number_in); // or std::erase_if(myNumbers, [&](int x) { return x == number_in; }); Prior to C++20, use the erase-remove idiom: std::vector<int>& vec = myNumbers; // use shorter name vec.erase(std::remove(vec.begin(), vec.end(), number_in), vec.end()); // or vec.erase(std::remove_if(vec.begin(), vec.end(), [&](int x) … Read more
Don’t forget that you can treat pointers as iterators: w_.assign(w, w + len);
This article gives more details about this issue: http://electrosofts.com/systemverilog/arrays.html, especially section 5.2. A packed array is a mechanism for subdividing a vector into subfields which can be conveniently accessed as array elements. Consequently, a packed array is guaranteed to be represented as a contiguous set of bits. An unpacked array may or may not be … Read more
The current std::vector doesn’t provide any capability or interface to take ownership of previously allocated storage. Presumably it would be too easy to pass a stack address in by accident, allowing more problems than it solved. If you want to avoid copying into a vector, you’ll either need to use vectors through your entire call … Read more