On Thu, 23 Feb 2012 18:42:51 +0100, Artur Skawina <art.08...@gmail.com>
wrote:
On 02/23/12 11:35, simendsjo wrote:
Say i have a c function (didn't include first format argument for
simplicity)
void print(...);
I wrap it up:
extern(System) void print(...);
And then I try to wrap it up in some safer D way:
void print(Args...)(Args args)
{
print(args); // only the first argument is printed
}
void print(...)
{
print(_argptr); // no go either
}
How am I supposed to do this? http://dlang.org/function.html#variadic
doesn't make my any smarter.
You may want to check if a va_list based version of the C function is
available.
Anyway, the above should work, with a valid C prototype; this works here:
------------------------------------------------------------------------------------------
import std.string;
extern (C) int printf(const char*, ...);
int dp(A...)(A args) { return printf(args); }
void main(string[] argv) {
dp(cast(char*)"%s\n", argv[0].toStringz);
dp(cast(char*)"%s, %s\n", argv[0].toStringz, argv[1].toStringz);
dp(cast(char*)"%s, %s, %s\n", argv[0].toStringz, argv[1].toStringz,
argv[2].toStringz);
dp(cast(char*)"%s, %d, %s\n", argv[0].toStringz, 42,
argv[2].toStringz);
}
------------------------------------------------------------------------------------------
and you can even do things like:
------------------------------------------------------------------------------------------
import std.string;
import std.typetuple;
extern (C) int printf(const char*, ...);
int dp(A...)(A args) {
alias ReplaceAll!(immutable(char)[], char*, A) CA;
CA cargs;
foreach (i, arg; args) {
static if (is(typeof(arg):const(char)[]))
cargs[i] = cast(char*)arg.toStringz;
else
cargs[i] = arg;
}
return printf(cargs);
}
void main(string[] argv) {
dp("%s\n", argv[0]);
dp("%s, %s\n", argv[0], argv[1]);
dp("%s, %s, %s\n", argv[0], argv[1], argv[2]);
dp("%s, %d, %s\n", argv[0], 42, argv[2]);
}
------------------------------------------------------------------------------------------
to expose a more sane API.
Note: this example only handles D strings.
BTW, is there a simpler and/or more generic way to achieve this?
Thinking about
using it in C bindings...
artur
Hmm. Didn't my previous post make it to the newsgroup? Is visible at my
end.
I wrote: "
My bad. The first version works just fine. I passed a float and had the
format string as %d..."
So
print(Args...)(Args args)
{
c_print(args); // works just fine
}
