types

问题 I need to find if a type is a certain generic type. class MyType<T> {} var instance = new MyType<int>(); var type = instance.GetType(); This check does not work, but this is what I want to check. If the type is of that generic type, regardless of what T is. type == typeof( MyType<> ) This does work, but feels dirty. It could also be wrong since it's not the FullName . type.Name == typeof( MyType<> ).Name I'm assuming there is a way to do this, but I haven't found one. Using IsAssignableFrom

问题 I want to write a type utility that omits fields recursively. Something that you would name and use like that OmitRecursively<SomeType, 'keyToOmit'> I've tried to do it using mapped types + conditional typing but I stuck on the case when all required fields got typed correctly (hence field disappeared from nested type), but optional fields are ignored with that approach. // This is for one function that removes recursively __typename field // that Appolo client adds type Deapolify<T extends {

问题 Why Console.WriteLine((1000000f + 0.10f).ToString("N2")); print 1 000 000.00 but no 1 000 000.10? When I use type "double" or type "float" less 1000000 - this problem disappears! 回答1: Use decimal to prevent those accuracy/rounding issues. Console.WriteLine((1000000m + 0.10m).ToString("N2")); Reason: float has only a accuracy of 7 digits (reference) - your number has 8 回答2: According to MSDN, float type has only 7 digits precision. One milion has 7 digits, decimal part is rounded. Double type

问题 While reading Data Types from the Rust Book I noticed that sometimes a variable is defined with a type annotation and sometimes not. When should I use type annotations? let tup: (i32, f64, u8) = (500, 6.4, 1); let tup = (500, 6.4, 1); let months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]; let a: [i32; 5] = [1, 2, 3, 4, 5]; 回答1: When types have to be specified If the compiler cannot infer the type by itself, it

问题 While reading Data Types from the Rust Book I noticed that sometimes a variable is defined with a type annotation and sometimes not. When should I use type annotations? let tup: (i32, f64, u8) = (500, 6.4, 1); let tup = (500, 6.4, 1); let months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]; let a: [i32; 5] = [1, 2, 3, 4, 5]; 回答1: When types have to be specified If the compiler cannot infer the type by itself, it

问题 Answer: In short use virtual functions! So don't actually use this as good design, but for learning purposes take a read! I want to start off by saying I am using c++ and Qt I have a vector of Shape pointers (Base class) Edit: doSomething() is not a member of the Base class but instead a derived class member. Which is why I am using dynamic_cast to get Shape* to the Derived* so that I can access it. I am really doing this just out of curiosity at this point though and for other peoples

问题 Answer: In short use virtual functions! So don't actually use this as good design, but for learning purposes take a read! I want to start off by saying I am using c++ and Qt I have a vector of Shape pointers (Base class) Edit: doSomething() is not a member of the Base class but instead a derived class member. Which is why I am using dynamic_cast to get Shape* to the Derived* so that I can access it. I am really doing this just out of curiosity at this point though and for other peoples

问题 In the example below the Default trait is used just for demonstration purposes. My questions are: What is the difference between the declarations of f() and g() ? Why g() doesn't compile since it's identical to f() ? How can I return a concrete type out of a impl trait generically typed declaration? struct Something { } impl Default for Something { fn default() -> Self { Something{} } } // This compiles. pub fn f() -> impl Default { Something{} } // This doesn't. pub fn g<T: Default>() -> T {

问题 Ran a benchmark and uint32_fast_t is 8 byte but slower than 4 byte uint32_t for nearly all operations. If this is the case why does uint32_fast_t not stay as 4 bytes? OS info: 5.3.0-62-generic #56~18.04.1-Ubuntu SMP Wed Jun 24 16:17:03 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux Cpu info: cat /sys/devices/cpu/caps/pmu_name skylake model name : Intel(R) Core(TM) i7-8565U CPU @ 1.80GHz Benchmark I used for testing: #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <cstdint>

问题 In plain untyped Javascript, it's not so hard to write a function which can operate on either numbers or bigints, depending on the arguments which are passed in: const sumOfSquares = (a,b) => a*a + b*b; sumOfSquares(3, 4); // returns 25 sumOfSquares(3n, 4n); // returns 25n sumOfSquares(3n, 4); // throws a TypeError It seems like there ought to be a way to declare this function in typescript so that the compiler will enforce that the arguments will work together. I tried const sumOfSquares =