ref: d90515c5036b9c62dedc9895c781c6459c872209
dir: /lib/thread/waitgrp.myr/
use std
use "atomic"
pkg thread =
	type waitgrp = struct
		_val : uint32
	;;
	const mkwg : (v : uint32 -> waitgrp)
	const wgwait : (w : waitgrp# -> void)
	const wgpost : (w : waitgrp# -> void)
;;
const mkwg = {v
	-> [._val = v]
}
const wgwait = {w
	for var i = 0; i < 1000; i++
		if xget(&w._val) == 0
			-> void
		;;
	;;
	for var i = 0; i < 1000; i++
		if xget(&w._val) == 0
			-> void
		;;
		std.nanosleep(10_000)
	;;
	for var i = 0; i < 1000; i++
		if xget(&w._val) == 0
			-> void
		;;
		std.nanosleep(100_000)
	;;
	for ; ;
		if xget(&w._val) == 0
			-> void
		;;
		std.nanosleep(1_000_000)
	;;
}
const wgpost = {w
	std.assert(xadd(&w._val, -1) > 0, "error: waitgroup underflowed\n")
}