Summary

Chapter summary

• The return type of an auto function is deduced automatically.

• The return value of a ref function is a reference to an existing variable.

• The return value of an auto ref function is a reference if possible, a copy otherwise.

• inout carries the const, immutable, or mutable attribute of the parameter to the return type.

• A pure function cannot access mutable global or static state. The compiler infers the purity of templates, delegates, anonymous functions, and auto functions.

• @nogc functions cannot involve GC operations.

• @safe functions cannot corrupt memory. The compiler infers the safety attributes of templates, delegates, anonymous functions, and auto functions.

• @trusted functions are indeed safe but cannot be specified as such; they are considered @safe both by the programmer and the compiler.

• @system functions can use every D feature. @system is the default safety attribute.

• Functions can be executed at compile time (CTFE) as well. This can be differentiated by the value of the special variable __ctfe.

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