Re: Make function alias
On Monday, 20 August 2018 at 13:14:14 UTC, Andrey wrote:
Hello,
I want to make an alias to function "std.stdio.writeln" and
"std.stdio.write" and use it like:
static void log(bool newline = true)(string text)
{
alias print(T...) = newline ? :
_file.print();
text.print();
}
Unfortunately, it doesn't work... Also tried with "enum print
..." but also no success.
How to do it correctly?
If it's about having a concise syntax then you can do:
---
import std.stdio;
void main()
{
log!false("meep ! ");
log!true("meep meep !");
}
static void log(bool newline = true)(string text)
{
alias print = (a) => newline ? writeln(a) : write(a);
print(text);
}
---
although this is like static if {} () else {}
Re: Make function alias
On Monday, 20 August 2018 at 13:35:07 UTC, ag0aep6g wrote: On 08/20/2018 03:14 PM, Andrey wrote: Thanks everybody for your answers.
Re: Make function alias
On 08/20/2018 03:14 PM, Andrey wrote:
Hello,
I want to make an alias to function "std.stdio.writeln" and
"std.stdio.write" and use it like:
static void log(bool newline = true)(string text)
{
alias print(T...) = newline ? :
_file.print();
text.print();
}
Unfortunately, it doesn't work... Also tried with "enum print ..." but
also no success.
How to do it correctly?
`writeln` is a template, so you can't do ``. You'd have to
instantiate the template before you can get the function pointer:
`!T`.
Even then you can't make an alias of that. `!T` is a function
pointer, which is a value. But aliases work on types and symbols, not
values.
If you manage to obtain aliases, you won't be able to use the ternary
operator on them. Being an expression, `foo ? bar : baz` works on
values. You can't use it with function aliases.
You have to commit to either function aliases or function pointers (values).
With aliases (no address-of operator, no ternary operator, `print` is
not a template):
void log(bool newline = true)(string text)
{
static if (newline) alias print = writeln;
else alias print = writeln;
print(text); /* Can't use UFCS with a local `print`, so
`text.print()` doesn't work. */
}
With function pointers (have to instantiate `writeln`, `write`, and `print):
void log(bool newline = true)(string text)
{
enum print(T ...) = newline ? !T : !T;
print!string(text); /* No IFTI, because `print` isn't a function
template. */
}
Re: Make function alias
On Monday, 20 August 2018 at 13:14:14 UTC, Andrey wrote:
Hello,
I want to make an alias to function "std.stdio.writeln" and
"std.stdio.write" and use it like:
static void log(bool newline = true)(string text)
{
alias print(T...) = newline ? :
_file.print();
text.print();
}
Unfortunately, it doesn't work... Also tried with "enum print
..." but also no success.
How to do it correctly?
Since newline is a compile-time parameter, you can use `static
if`:
static if (newline) {
alias print = writeln;
} else {
alias print = write;
}
Note that since this alias is local to the function, you cannot
use it with UFCS, so you will have to write `print(text)` instead
of `text.print()`.
Full example: https://run.dlang.io/is/SrBJdk
Re: Make function alias
On Monday, 20 August 2018 at 13:22:02 UTC, Andrey wrote:
On Monday, 20 August 2018 at 13:14:14 UTC, Andrey wrote:
Mistake... this is:
static void log(bool newline = true)(string text)
{
alias print(T...) = newline ? :
_file.print(text);
text.print();
}
static void log(bool newline = true)(string text)
{
static if(newline)alias print = writeln;
else alias print = write;
_file.print(text);
text.print();
}
Re: Make function alias
On Monday, 20 August 2018 at 13:14:14 UTC, Andrey wrote:
Mistake... this is:
static void log(bool newline = true)(string text)
{
alias print(T...) = newline ? :
_file.print(text);
text.print();
}
