[Impromptu] Formatting strings (printf-style)

[Glen F]

Hi there -- a quick question: how to format strings?  I've tried  
using NSString, but I'm not super-familiar with the ObjC bridge...   
It doesn't seem to want to work with "stringWithFormat:", which takes  
a variable number of arguments.  Impromptu returns "too many  
arguments passed, ignoring additional arguments".

What am I doing wrong?

;----------
(define nsstring (objc:call "NSString" "stringWithFormat:" "rounded:  
%.2f" 3.14159))
(print nsstring)
;----------

This prints out (besides the logged warning about 'too many arguments'):

#<OBJC: rounded: 0.00>

Thanks,
Glen.