You can use num or num-traits crates and bound your generic function type with num::Float, num::Integer or whatever relevant trait: use num::Float; // 0.2.1 fn main() { let f1: f32 = 2.0; let f2: f64 = 3.0; let i1: i32 = 3; println!(“{:?}”, sqrt(f1)); println!(“{:?}”, sqrt(f2)); println!(“{:?}”, sqrt(i1)); // error } fn sqrt<T: Float>(input: T) … Read more
In order to solve this problem with templates, you have to use a template template parameter. Unfortunately, you cannot pass template template function as a type, because it has to be instantiated first. But there is a workaround with dummy structures. Here is an example: template <typename T> struct a { static void foo (T … Read more
As of Fri, 7 Aug 2015 01:44:49 -0400 (05:44 +0000) concepts support has been merged into gcc’s trunk. Using a build from after that point, you can enable concepts support with the -std=c++1z flag. As of gcc 6.1 (27-04-2016), concepts are enabled by -fconcepts as they are unlikely to be included in C++17, so they … Read more
That’s an optional template parameter with no name and a default value. It’s used to apply the enable_if condition; it will create a compiler error if the condition is not met. You can use exactly the same syntax for normal method arguments.
I would like tag dispatch because: Easy to extend with new tags Easy to use inheritance (example) It is fairly common technique in generic programming It seems tricky to me to add third variant in second example. When you’ll want to add, for example non-POD-of-PODs type you’ll have to replace bool in template <typename T, … Read more
Data.Typeable is an encoding of an well known approach (see e.g. Harper) to implementing delayed (dynamic) type checking in a statically typed language — using a universal type. Such a type wraps code for which type checking would not succeed until a later phase. Rather than reject the program as ill-typed, the compiler passes it … Read more
The problem is that type arguments are erased, so you can’t check against the full type Map, because at runtime there’s no information about those String and Any. To work around this, use wildcards: if (value is Map<*, *>) {…}
The other answers are totally fine: One does not need a special syntax to support generics in Python Python uses duck typing as pointed out by André. However, if you still want a typed variant, there is a built-in solution since Python 3.5. A full list of available type annotations is available in the Python … Read more