More Format Directives

A friend of mine Jorg Preisendorfer, came across my entries on format directives. The modifiers for iteration as mentioned in section 22.3.7.4 of CLHS. I had discovered "~{" and "~}" directives. Here are the more elegant rewrites.

My code

 (format t "~{~{~A~%~A~%~}~}" '((a b) (c d) (e f) (g h)))

The better version

 (format t "~:{~A~%~A~%~}" '((a b) (c d) (e f) (g h)))

More succinct, and easier to write. The colon performs the iteration on sublists.

Another directive that I had discovered was "~R" which prints a number in the English formulation. I had also requested a Loop version mainly because of my inexperience with Loop. Here is the code.

  (loop for x = (expt 10 9) then (* x 1000)

   		until (>= x (expt 10 66))

   do (format t "~R = ~:*~A~%" x))

The directive "~:*" directive is also very interesting as mentioned in section 22.3.7.1 of the CLHS.

Thanks for the responses Jorg.