Naming convention for template parameters

[Timothee Cour]

On Mon, Jul 15, 2013 at 4:02 PM, H. S. Teoh <hsteoh at quickfur.ath.cx> wrote:

> On Tue, Jul 16, 2013 at 12:52:21AM +0200, Joseph Rushton Wakeling wrote:
> > Hello all,
> >
> > Quick query -- what's the preferred template variable name for a range
> type?
> >
> > I've seen both R and Range used as options but want to confirm if
> there's a
> > preference for one or the other.  It occurs to me that Range might
> potentially
> > clash with some library or user-created entity.
> [...]
>
> I don't think it matters in this case, as the name would only be visible
> within the scope of the template, and AFAICT would shadow any external
> definitions, so you shouldn't get into trouble with it.
>
> I generally use R 'cos it's less typing and I'm lazy, but Walter has
> been recently of the opinion that a more descriptive name is necessary
> for ddoc purposes, e.g., MyStruct(InputRange)(InputRange r) is much more
> self-documenting than MyStruct(R)(R r). Template signatures aren't
> included in ddoc output IIRC, so this can be an important consideration.
>
>
Using Range is vague (inputRange? etc) anyways so might as well use R.
Including template constraints in generated doc would make this a non-issue.

I don't understand the rationale for not including them. I've raised the
issue before, see [1].

For example in http://dlang.org/phobos/std_algorithm.html we have:

----
void reverse(Range)(Range r);

void reverse(Range)(Range r);
----
which is really not helpful.
It should show full signature:

----
void reverse(Range)(Range r) if (isBidirectionalRange!Range &&
!isRandomAccessRange!Range && hasSwappableElements!Range)

void reverse(Range)(Range r) if (isRandomAccessRange!Range &&
hasLength!Range)
----

and even better, with shorter type:
----
void reverse(R)(R r) if (isBidirectionalRange!R && !isRandomAccessRange!R
&& hasSwappableElements!R)

void reverse(R)(R r) if (isRandomAccessRange!R && hasLength!R)
----



[1]: implicit template constraint notation :
http://forum.dlang.org/post/mailman.1006.1370836279.13711.digitalmars-d@puremagic.com
).
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