you can think of it as a sort of .. intelligent, type-safe macro. but only sort of.

mixins are expanded (inlined) when they are used, so you can use it to insert code.

void PrintMessage() { writefln("message!"); }

template Fork { PrintMessage(); }

void main()
{
mixin Fork;

}

a pretty useless example, but it will call PrintMessage() when you use mixin Fork. it's because it expands inline so the mixin Fork line in main() becomes:

PrintMessage();

the more interesting stuff you can do with a mixin is when you use parameters.

template Spoon(T) { T num; }

void main()
{

mixin Spoon!(float);

num=5.5;

}

personally i don't use them that often and i think they are of limited usefulness.. but they're there. and they're interesting.