Double floats cause issues with the compiler md> (setf *read-default-float-format* 'double-float) double-float md> (ps '(1.0 2.0 3.0)) "[1.0D0, 2.0D0, 3.0D0];" since 1.0D0 isn't javascript This is a simpler example: md> (ps 1.0D0) "1.0D0;" Adding... (defmethod ps-print ((x double-float)) (format *psw-stream* "~F" (coerce x 'single-float))) to printer.lisp resolves the problem. At which point it's tempting to rework the ps-print method on number with: (defmethod ps-print ((x double-float)) (format *psw-stream* "~F" (coerce x 'single-float))) (defmethod ps-print ((x integer)) (format *psw-stream* "~D" x)) (defmethod ps-print ((x number)) (format *psw-stream* "~F" x)) Thanks for this awesome tool! - ben