Chapter 96: Type Inference

This topic discusses about type inferencing that involves the keyword auto type that is available from C++11.

Section 96.1: Data Type: Auto

This example shows the basic type inferences the compiler can perform.

However, the auto keyword does not always perform the expected type inference without additional hints for & or const or constexpr

//y = unsigned int,

//note that y does not infer as const unsigned int&

//The compiler would have generated a copy instead of a reference value to e or b auto y = e;

Section 96.2: Lambda auto

The data type auto keyword is a convenient way for programmers to declare lambda functions. It helps by shortening the amount of text programmers need to type to declare a function pointer.

auto DoThis = [](int a, int b) { return a + b; };

//Do this is of type (int)(*DoThis)(int, int)

//else we would have to write this long

int(*pDoThis)(int, int)= [](int a, int b) { return a + b; };

//using 'auto' shortens the definition for lambda functions

By default, if the return type of lambda functions is not defined, it will be automatically inferred from the return expression types.

These 3 is basically the same thing

[](int a, int b) -> int { return a + b; }; [](int a, int b) -> auto { return a + b; }; [](int a, int b) { return a + b; };

Section 96.3: Loops and auto

This example shows how auto can be used to shorten type declaration for for loops

std::map<int, std::string> Map;