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 ? &writeln : &write;
_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 `&writeln`. You'd have to
instantiate the template before you can get the function pointer:
`&writeln!T`.
Even then you can't make an alias of that. `&writeln!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 ? &writeln!T : &write!T;
print!string(text); /* No IFTI, because `print` isn't a function
template. */
}
----
