Since there has been some activity I want to share this warning. In older version of Applescript (before 10.7) set n to "4.1" set n to -n would yield -4.1 Under 10.7 and 10.8 it yields -4 It seems the default coercion is to integer rather than number. bizarrely, set n to -1 * n yields -4.1 -Mark Fixed my code, Documented my fixes, Filed a bug report.