Prime Sieve - Plan 9 rc script

filter.rc

# prime sieve based on https://swtch.com/~rsc/talks/threads07/
# primes appear on stderr
# example:
# 	seq 2 100 | filter

fn filter {
	p=`{read -n 1}
	if (~ $status '') {
		echo $p >[1=2]
		x=`{read -n 1}
		while (~ $status '') {
			if (test `{echo $x '%' $p | hoc} -ne 0) echo $x
			x=`{read -n 1}
		}
	} | filter
}