t | A command-line todo/task tool | Command Line Interface library

You can check all the types are identical or not with the help of fold expression (since C++17).

E.g.

The issue you are having has nothing to do with templates. You cannot invoke std::async() on a member function without binding it to an instance. Wrapping the call in a lambda does the trick.

Here's an example:

I haven't come across such a ConcurrentCounter library, but crates.io is huge, maybe you find something. However, if you are mostly concerned with primitives such as i32, there is a better alternative call: Atomics, definitely worth checking out.

Nevertheless, your approach of generalizing the ConcurrentCounter is going in a good direction. In the context of operation overloading, std::ops is worth a look. Specifically, you need Add, Sub, and Mul, respectively. Also, you need a Copy bound (alternatively, a Clone would also do). So you were pretty close:

This compact fragment satisfies the queries you listed

I modified your code.this will works fine
but the customerMian() and adminMain() function not defined.

Consider this awk:

So, this is a good opportunity to use purrr::map. You are half way there by applying code to one dataframe.

You can take the code that you have written above and put it into a function.

A functional approach would be (but probably not clean)

The entire data from beneficiaryInfo array is removed because your del function does just that. If you want to just remove a particular object from the array, you need to use the index or the id (if it has).

In the template declare the index and pass it as an argument to your delete method so you can remove from the list the object at that index.