{TRUE}
	var b = FALSE;
	if (b(g(t, head(s)) != NULL) then
		if (size(s) == 1) then
			{size(s)  = 1}
			b = b(g(t, head(s));
		else if (size(s) > 1) then
			{size(s) > 1}
			b = checkword(g(t, head(s)), tail(s))
			{b = in(g(t, head(s)), tail(s))}
		fi
		{b = in(t, tail(s))}
	fi

{b = in (t, s)}