Hello, World! (page 4)

On Wed, Mar 30, 2022 at 06:50:40PM +0000, Max Samukha via Digitalmars-d wrote: > On Wednesday, 30 March 2022 at 15:49:08 UTC, H. S. Teoh wrote: [...] > > And pragma(msg) is technically not your program outputting the > > message, but the compiler. You need to put it in main() for a proper > > implementation of Hello World. ;-) [...] > template add(int x) > { > pragma(msg, x); > int add(int y) > { > import std.stdio: writeln; > writeln(y); > return x + y; > } > } > > void main() > { > auto z = add!1(2); > } > > Is this a program that starts at compile time and continues at run time, or a meta-program that generates another program? ) [...] It's a program with a split personality that prints half its output at compile time and the other half at runtime. :-D If you only compile but never run it, then you only get half of its output, and if you run it multiple times you get redundant output. :-P T -- The two rules of success: 1. Don't tell everything you know. -- YHL

March 31, 2022

Re: Hello, World!

Posted by Tejas
in reply to Max Samukha

Permalink

Tejas

Posted in reply to Max Samukha

Permalink

On Wednesday, 30 March 2022 at 18:50:40 UTC, Max Samukha wrote:

On Wednesday, 30 March 2022 at 15:49:08 UTC, H. S. Teoh wrote:

And pragma(msg) is technically not your program outputting the message,
but the compiler. You need to put it in main() for a proper
implementation of Hello World. ;-)

template add(int x)
{
pragma(msg, x);
int add(int y)
{
import std.stdio: writeln;
writeln(y);
return x + y;
}
}

void main()
{
auto z = add!1(2);
}

Is this a program that starts at compile time and continues at run time, or a meta-program that generates another program? )

It's a normal template... what are you talking about??

1
2
3
import object;
template add(int x)
{
	pragma (msg, x);
	int add(int y)
	{
		return x + y;
	}
}
extern (C) extern (C) void main()
{
	add(2);
	add(1);
	add(0);
	return 0;
}
add!1
{
	pure nothrow @nogc @safe int add(int y)
	{
		return 1 + y;
	}

}
add!2
{
	pure nothrow @nogc @safe int add(int y)
	{
		return 2 + y;
	}

}
add!3
{
	pure nothrow @nogc @safe int add(int y)
	{
		return 3 + y;
	}

}

(Took the output from the "AST" option in run.dlang.io)
(Used -betterC to strip away boilerplate stuff)

On Wednesday, 30 March 2022 at 20:05:07 UTC, H. S. Teoh wrote: > > It's a program with a split personality that prints half its output at compile time and the other half at runtime. :-D > > If you only compile but never run it, then you only get half of its output, and if you run it multiple times you get redundant output. :-P > > > T That's the way to think about it. Thanks! )

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