--
-- This one is for text arguments
--
drop function bitstring2days(text);
create function bitstring2days(text) returns text
as '
	set result ""
	foreach bit [split $1 {}] day {S M T W T F S} {
		if {"$bit" == "1"} {
			append result $day
		} else {
			append result "-"
		}
	}
	return $result
' language pltcl;

--
-- This one for if your actual days bits are in an integer
--
drop function bitint2days(integer);
create function bitint2days(integer) returns text
as '
	set result ""
	binary scan [binary format c $1] B8 bits
	foreach bit [split [string range $bits 1 end] {}] day {S M T W T F S} {
		if {"$bit" == "1"} {
			append result $day
		} else {
			append result "-"
		}
	}
	return $result
' language pltcl;

select bitstring2days('1100111');
select bitint2days(103);