Flag & byLine confusion.

[Paul Backus]

On Saturday, 19 December 2020 at 23:16:00 UTC, Rekel wrote:
> After reading most of the tour.dlang.org website, I was 
> completely surprised & confused encountering 'KeepTerminator', 
> a 'Flag' used by the File.byLine function. With no examples 
> denoting how to use it.
>
> Most confusing was the way the documentation (website & 
> in-editor) used;
> 1. Yes.keepTerminator
> 2. KeepTerminator.yes
> 3. Flag!"keepTerminator".yes
> & Don't get me started on the autocomplete trying to get me to 
> use KeepTerminator.Flag.yes (VSCode & code-d)

Flag is a templated enum, documented here:

http://phobos.dpldocs.info/std.typecons.Flag.html

It has two members, Flag!"name".yes and Flag!"name".no. As 
explained in the documentation linked above, Yes and No are 
structs that provide (slightly) less verbose aliases for these 
enum members. The documentation for Yes and No is here:

http://phobos.dpldocs.info/std.typecons.Yes.html
http://phobos.dpldocs.info/std.typecons.No.html

> Even further confused by the in-editor documentation, is this 
> function a template?:
> "
> byLine(Terminator = char, Char = char) (KeepTerminator 
> keepTerminator = No,keepTerminator, Terminator terminator = 
> '\\n')
> "

Yes, it is a template. If you look at the section on "parameters" 
in the documentation

http://phobos.dpldocs.info/std.stdio.File.byLine.1.html#parameters

...you can see that the template parameter Char is the character 
type used for the lines. So if you wanted to have lines of wchar 
instead of char, you could use `.byLine!(wchar, wchar)`.