Re: If statements and unused template parameters in Phobos documentation

[Rekel via Digitalmars-d-learn]

On Sunday, 20 December 2020 at 13:58:00 UTC, Max Haughton wrote:

The if is a template constraint.


Ah sorry! I must have missed that part of the dlang tour.
(https://tour.dlang.org/tour/en/gems/template-meta-programming)

Thanks a lot!

Re: If statements and unused template parameters in Phobos documentation

[Max Haughton via Digitalmars-d-learn]

On Sunday, 20 December 2020 at 13:51:08 UTC, Rekel wrote:
I found a lot of the Phobos documentation to contain template 
arguments and if statements that made no sense to me, for 
example:


```
 uint readf(alias format, A...) (
 auto ref A args
)
if (isSomeString!(typeof(format)));

uint readf(A...) (
 scope const(char)[] format,
 auto ref A args
);
``` https://dlang.org/library/std/stdio/file.readf.html

From stdio.readf & stdio.File.readf. I'm assuming this is some 
kind of template, but often it seems there are more parameters 
in the first '()' part than are ever given. Am I missing 
something? Additionally, what is that if statement for? It 
precedes nothing.


The if is a template constraint.

If statements and unused template parameters in Phobos documentation

[Rekel via Digitalmars-d-learn]

I found a lot of the Phobos documentation to contain template 
arguments and if statements that made no sense to me, for example:


```
 uint readf(alias format, A...) (
 auto ref A args
)
if (isSomeString!(typeof(format)));

uint readf(A...) (
 scope const(char)[] format,
 auto ref A args
);
``` https://dlang.org/library/std/stdio/file.readf.html

From stdio.readf & stdio.File.readf. I'm assuming this is some 
kind of template, but often it seems there are more parameters in 
the first '()' part than are ever given. Am I missing something? 
Additionally, what is that if statement for? It precedes nothing.