How to instantiate a map with multiple functions

[Jay Norwood via Digitalmars-d-learn]

On Sunday, 27 December 2015 at 03:22:50 UTC, Jay Norwood wrote:
> I would probably want to associate names with the tuple metric 
> results, and I've seen that somewhere in the docs in parameter 
> tuples.   I suppose I'll try those in place of the current 
> tuple ...
>

This worked to associate names with the tuple values. Just the 
one line modified.
samples.each!((int i, ref 
a)=>tuple!("sample","f1","f2","f3")(i,f1(a),f2(a),f3(a)).writeln());

======= output
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(0, 
3, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(1, 
6, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(2, 
9, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(3, 
12, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(4, 
15, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(5, 
18, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(6, 
21, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(7, 
24, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(8, 
27, 0.7, 0.8)
Tuple!(int, "sample", ulong, "f1", double, "f2", double, "f3")(9, 
30, 0.7, 0.8)