I think templates get used a lot as a way to reuse container types that have a lot of algorithmic values such as dynamic-arrays (vectors), maps, trees, etc. sorting, etc.

Without templates, necessarily, these contain implementations are written in a generic way and are given just enough information about the type required for their domain. For instance, with a vector, they just need the data to be blt'able and they need to know the size of each item.

Let's say you have a container class called Vector that does this. It takes void*. The simplistic usage of this would be for the application layer code to do a lot of casting. So if they are managing Cat objects, they have to cast Cat* to void*, and back all over the place. Littering application code with casts has obvious problems.

Templates solve this.

Another way to solve it is to create a custom container type for the type your storing in the container. So if you have a Cat class, you'd create a CatList class derived from Vector. You then overload the few methods that you use and introduce versions that take Cat objects instead of void*. So you'd overload the Vector::Add(void*) method with Cat::Add(Cat*), which internally simply passes the parameter to Vector::Add().

The other approach, the only example of which I recall from the early 90s with a large application framework, is to use a custom utility that creates these types over classes. I believe MFC did this. They had different classes for containers like CStringArray, CRectArray, CDoulbeArray, CIntArray, etc. Rather than maintain duplicate code, they did some type of meta-programming similar to macros, using an external tool that would generate the classes. They made the tool available with Visual C++ in case anyone wanted to use it -- I never did. Maybe I should have. But at the time, the experts were touting, "Sane subset of C++" and "You don't need Templates"

I think templates get used a lot as a way to reuse container types that have a lot of algorithmic values such as dynamic-arrays (vectors), maps, trees, etc. sorting, etc.

Without templates, necessarily, these contain implementations are written in a generic way and are given just enough information about the type required for their domain. For instance, with a vector, they just need the data to be blt'able and they need to know the size of each item.

Let's say you have a container class called Vector that does this. It takes void*. The simplistic usage of this would be for the application layer code to do a lot of casting. So if they are managing Cat objects, they have to cast Cat* to void*, and back all over the place. Littering application code with casts has obvious problems.

Templates solve this.

Another way to solve it is to create a custom container type for the type you're storing in the container. So if you have a Cat class, you'd create a CatList class derived from Vector. You then overload the few methods that you use, introducing versions that take Cat objects instead of void*. So you'd overload the Vector::Add(void*) method with Cat::Add(Cat*), which internally simply passes the parameter to Vector::Add(). Then in your application code, you'd call the overloaded version of Add when passing in a Cat object and thus avoid casting. To be fair, the Add method wouldn't require a cast because a Cat* object converts to void* without a cast. But the method to retrieve an item, such as the index overload or a Get() method would.

The other approach, the only example of which I recall from the early 90s with a large application framework, is to use a custom utility that creates these types over classes. I believe MFC did this. They had different classes for containers like CStringArray, CRectArray, CDoulbeArray, CIntArray, etc. Rather than maintain duplicate code, they did some type of meta-programming similar to macros, using an external tool that would generate the classes. They made the tool available with Visual C++ in case anyone wanted to use it -- I never did. Maybe I should have. But at the time, the experts were touting, "Sane subset of C++" and "You don't need Templates"