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This article mainly introduces "how C++ uses templates to express containers and ranges". In daily operation, I believe many people have doubts about how C++ uses templates to express containers and ranges. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the doubts about "how C++ uses templates to express containers and ranges". Next, please follow the editor to study!

T.3: use templates to represent containers and ranges

Reason (reason)

Containers need an element type, and expressing that as a template argument is general, reusable, and type safe. It also avoids brittle or inefficient workarounds. Convention: That's the way the STL does it.

The container needs to know the element type, and it is common, reusable, and type safe to represent the element type as a template parameter. It can avoid vulnerability and inefficient flexibility. As a rule, that's what STL does.

Example (sample)

Template

/ / requires Regular

Class Vector {

/ /...

T * elem; / / points to sz Ts

Int sz

}

Vector v (10)

V [7] = 9.9 × example, bad (negative example) class Container {

/ /...

Void* elem; / / points to size elements of some type

Int sz

}

Container c (10, sizeof (double))

(double*) c.elem) [7] = 9.9

This doesn't directly express the intent of the programmer and hides the structure of the program from the type system and optimizer.

Hiding the void* behind macros simply obscures the problems and introduces new opportunities for confusion.

This code does not directly express the programmer's intention and hides the program structure from the type system and optimizer. Masking void* with macro definitions will only blur the problem and further increase the chances of confusion.

Exceptions: If you need an ABI-stable interface, you might have to provide a base implementation and express the (type-safe) template in terms of that. See Stable base.

Exception: if you need a stable interface for ABI, you may have to provide a basic implementation and represent the template according to its concept.

Enforcement (implementation recommendations)

Flag uses of void*s and casts outside low-level implementation code

Marks cases where void* is used and low-level type conversions are used in the external implementation code.

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