I’m trying to create a simple template function which takes a callable object and a couple of int values, and returns the result of invoking the callable with those values. How do I get the function to figure out the return value’s type, and also be able to create such a type with its default… Read More C++ template function deducing return type
When iterating over an unordered map of values, std::unordered_map<Foo, Bar>, it will use an iterator pointing to values instd::pair<Foo, Bar>. This makes it seem like std::unordered_map stores its values internally as std::pairs of values. If I’m not mistaken, std::unordered_map works by hashing the key and using that for lookups. So, if the internal structure is… Read More How does std::unordered_map find values?
For ex- if we have an array A ={1, 2 , 3, 4, 5} and I want to find max element between A[i] and A[i+k]. Can I use max function for that , I tried to use it but I can’t. Please tell me if they any other way to do it. I need to… Read More Can we use std::max in cpp for finding maximum element in a subbarray?
So I tried to take input into the same variable called input with a loop. It behaves in a way that I do not know why. Here is the snippet use std::io::stdin; fn main(){ println!("Please Give Input: "); let mut input = String::new(); loop{ stdin().read_line(&mut input).expect("Error While Input"); print!("{input}"); } } on the first input… Read More Rust taking input in the same variable more than once behavior. Can anyone explain?
Consider the following code (clang). It has two identical loops explicitly terminated on the first iteration. One of them throws a warning (an error if -Wpedantic -Werror). The other does not. Trying to understand why. The code can be tested on Godbolt here template <typename K, typename V> int get(const std::map<K, V>& m) { for… Read More unreachable-code-loop-increment warning rules
my code copies the map in the same order map <string, int> to vector <string, int> I want this instead map <string, int> to vector <int, string> is it possible with std copy? #include <iostream> #include <vector> #include <map> #include <iterator> #include <fstream> using namespace std; int main(){ fstream fs; fs.open("test_text.txt"); if(!fs.is_open()){ cout << "could… Read More how to copy a map <string, int> into a vector <int, string>
I have output that looks like this: BTC-USDT [FTX] 20460.91 20470.09 BTC-USDT [BINANCE_US] 20457.34 20467.28 BTC-USDT [BINANCE_US] 20457.50 20467.28 I would like it to look like this: BTC-USDT [ FTX] 20460.91 20470.09 BTC-USDT [BINANCE_US] 20457.34 20467.28 BTC-USDT [BINANCE_US] 20457.50 20467.28 I think I am close with this code, but I am confused by setw() std::cout… Read More How to guarantee that std::cout always uses n width
[Solved] Thank you all, I didn’t even know about user-defined conversion function and how it works. Why it’s possible to use std::reference_wrapper::operator+=, if such operator does not exist, are there some implicit conversions? #include <iostream> #include <functional> #include <boost/type_index.hpp> using boost::typeindex::type_id_with_cvr; template <typename C> void test(C c) { c += 1; } int main() {… Read More How can std::reference_wrapper<int> use opretor += if std::reference_wrapper doesn't have operator+=
I try to understand the docs for std::less, where the following example is given for the usage with a template. #include <functional> #include <iostream> template <typename A, typename B, typename C = std::less<>> bool fun(A a, B b, C cmp = C{}) { return cmp(a, b); } int main() { std::cout << std::boolalpha << fun(1,… Read More C++ : curly brackets with std library type
I tried to understand the working of std::is_polymorphc in C++. This is defined in type_traits.h: template <class _Ty> struct is_polymorphic : bool_constant<__is_polymorphic(_Ty)> {}; // determine whether _Ty is a polymorphic type template <class _Ty> _INLINE_VAR constexpr bool is_polymorphic_v = __is_polymorphic(_Ty); I am not able to find the source code for __is_polymorphic. Could someone help me… Read More How does std::is_polymorphic identify polymorphism?