problem with byLine

[Chris Cain]

On Tuesday, 15 May 2012 at 18:54:51 UTC, dcoder wrote:
> Okay thanks alot Matt and Ali, that helps alot, but I still 
> don't
> get the dot in ".map" from the line above.  Doesn't the dot mean
> that .map is a member or a member function of the return value 
> of
> byLine()?  Which, in this case is struct ByLine?
>
> thanks.

A newer feature of D, UFCS (or Uniform Function Call Syntax) 
makes it so that you can use the dot syntax to mean either a 
member or member function OR it rewrites the call using the thing 
before the dot as the first parameter.

Let me show you what I mean:

struct S {
    int memberFunc() { return 0; }
}
int normFunc(S firstParam) { return 1; }

S s;
s.memberFunc(); // Calls the member function in S
s.normFunc(); // Rewritten to normFunc(s);



So in the examples they gave above, this is actually what is 
executed:
f.byLine().map!"a.idup"().array();
array(map!"a.idup"(f.byLine()));

So, as you can see f has the byLine member function, but the 
ByLine struct does not have a map function, so it's rewritten 
like that. Also, the Range returned by map does not have an array 
function, so it's rewritten again as the first parameter. As you 
can see, it would normally have to be read backwards (and with a 
bunch of parentheses to match), which can be confusing... while:
     f.byLine().map!"a.idup"().array();
Is more natural to read (by most) ... you're taking the lines, 
using the a.idup function on each, and then making an array from 
those elements.