*! xparse -- low-level parse into tokens, exclusive of parsing characters
*! version 1.0     Sean Becketti     January 1996		(STB-29: ip12)
program define xparse
version 4.0
quietly {
	global S_1
	local options "Parse(str) String(str)"
	parse "`*'"
	parse "`string'", parse(" `parse'")
	local string "`*'"
	local parse = trim("`parse'")
	local l = length("`parse'")
	parse "`string'", parse(" ")
	local n : word count `*'
	local i 0
	while `i'<`n' {
		local i = `i' + 1
		local parschr = 0
		local j = 0
		while `j'<`l' {
			local j = `j' + 1
			local p = substr("`parse'",`j',1)
			local parschr = `parschr' | index("`p'","``i''")
		}
		if !`parschr' { global S_1 "$S_1 ``i''" }
	}
}
end