question on map

[Alain De Vos via Digitalmars-d-learn]

As oppposed to what i expect code below prints nothing nothing on 
the screen. What is wrong and how to fix it ?
```
import std.stdio;
import std.range:iota;
import std.algorithm:map;
bool mywriteln(int x){
        writeln(x);
        return true;
}

void main(){
        5.iota.map!mywriteln;
}

```