• Paul (47/47) Dec 16 2022 I see code like this from time to time. Are the leading
• user1234 (5/10) Dec 16 2022 The only important thing you should know about is that doubly
• Adam D Ruppe (12/14) Dec 17 2022 The code you linked is a copy/paste from some C runtime library
• Paul (1/1) Dec 19 2022 Much appreciated...

Paul <phshaffer gmail.com> writes:

I see code like this from time to time.  Are the leading 
underscores significant, in general, in the D language?  Is it 
just programmer preference? Is it a coding practice, in general, 
that is common...even outside of D?  Thanks for any assistance.

From: 
http://dpldocs.info/this-week-in-d/Blog.Posted_2022_10_10.html#hello-arduino

```d
import ldc.llvmasm;

// Ports from the delay_basic.h in the thing
void _delay_loop_1(ubyte __count) {
	// this template param is required to avoid
	// assertion `!Call.getType()->isVoidTy() && "Bad inline asm!"' 
failed.

         __asm!ubyte (
                 "1: dec $0\n\tbrne 1b",
                 "=r,0", (__count)
         );
}
void _delay_loop_2(ushort __count) {
         __asm!ushort (`
	1: sbiw $0,1
	brne 1b
	`,
	`=w,0`,
	__count);
}

// port from delay.h in arduino thing
enum F_CPU = 1_000_000UL;

// this was _delay_ms but i did something wrong and changed 
double to int and i still don't love it
void _delay(int __ms) {
	ushort __ticks;
	ulong __tmp = (F_CPU * __ms) / 4000;
	if(__tmp < 1)
		__ticks = 1;
	else if(__tmp > 65_535) {
		__ticks = cast(ushort) (__ms * 10.0);
		while(__ticks) {
			_delay_loop_2(cast(ushort) (((F_CPU) / 4e3) / 10));
			__ticks--;
		}
		return;
	} else
		__ticks = cast(ushort) __tmp;
	_delay_loop_2(__ticks);
}
```

user1234 <user1234 12.de> writes:

On Saturday, 17 December 2022 at 02:42:22 UTC, Paul wrote:
 I see code like this from time to time.  Are the leading 
 underscores significant, in general, in the D language?  Is it 
 just programmer preference? Is it a coding practice, in 
 general, that is common...even outside of D?  Thanks for any 
 assistance.

The only important thing you should know about is that doubly 
leading underscores are reserved for symbols generated by the D 
front-end, so you should avoid them. This is specified here: 
https://dlang.org/spec/lex.html#identifiers.

Adam D Ruppe <destructionator gmail.com> writes:

On Saturday, 17 December 2022 at 02:42:22 UTC, Paul wrote:
 Are the leading underscores significant, in general, in the D 
 language?

The code you linked is a copy/paste from some C runtime library 
code, where the leading __ is the convention to indicate it is 
part of the private platform implementation, which user code 
shouldn't use. This ensures no name conflicts.

D has this rule too, you're actually not supposed to use __ 
prefixes in your own code either, since the compiler will use it 
for auto-generated names. But since it was a copy paste, I was 
too lazy to change it.

A single leading _ is sometimes used by some programmers to 
indicate private members, but that's no special meaning in the 
language.

Paul <phshaffer gmail.com> writes:

Much appreciated...