Re: Differences between lambda function and regular functions in higher order functions

[partypooper via Digitalmars-d-learn]

On Monday, 21 February 2022 at 10:04:16 UTC, steve wrote:
I am trying to implement a simple map function. I found code to 
do this in another post but it only seems to work with lambda 
functions and I do not understand why. Any help would be 
greatly appreciated

```
import std.stdio;

T[] map_vals(T,S)(scope T function(S) f, S[] a){
    auto b = new T[a.length];
    foreach(i,x;a) b[i] = f(x);
    return b;
}


auto timestwo(float x) {
    return 2*x;
    }

void main(){
    float[] my_array = [1., 2., 3.];
    auto ff = (float x)=>2*x;

    // This works
    writeln(map_vals(ff, my_array));

    // this does not
    // writeln(map_vals(timestwo, my_array));
}
```

I guess because your function parameter is actually a pointer to 
a function. ff is a pointer to anonymous function. timestwo is 
not. This should work

```d
writeln(map_vals(&timestwo, my_array));
```