mixin template question

lobo via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Sat Apr 11 21:04:42 PDT 2015


On Sunday, 12 April 2015 at 03:51:03 UTC, Paul D Anderson wrote:
> I don't understand why the following code compiles and runs 
> without an error:
>
> import std.stdio;
>
> mixin template ABC(){
>   int abc() { return 3; }
> }
>
> mixin ABC;
>
> int abc() { return 4; }
>
> void main()
> {
>   writefln("abc() = %s", abc());
> }
>
> Doesn't the mixin ABC create a function with the same signature 
> as the "actual function" abc()?
>
> It compiles with both included and writes "abc() = 4". If I 
> comment out the actual function then it writes "abc() = 3". The 
> actual function takes precedence, but why don't they conflict?
>
> Paul

As the manual says (snippet below) the surrounding scope 
overrides mixin

http://dlang.org/template-mixin.html

---
Mixin Scope
The declarations in a mixin are ‘imported’ into the surrounding 
scope. If the name of a declaration in a mixin is the same as a 
declaration in the surrounding scope, the surrounding declaration 
overrides the mixin one:
int x = 3;

mixin template Foo()
{
     int x = 5;
     int y = 5;
}

mixin Foo;
int y = 3;

void test()
{
     writefln("x = %d", x);  // prints 3
     writefln("y = %d", y);  // prints 3
}
---

bye,
lobo


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