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Don't forget that floating point numbers are just rational approximations, you can't get around issues of precision. CL-USER> (integer-decode-float .2d0) 7205759403792794 -55 1 CL-USER> (integer-decode-float .2) 13421773 -26 1 Your implementation may not have the exact same representations as mine, ...

I am not making a double copy. As far as I understood, :displaced-to makes the new array a kind of alias for the original array (or possibly a sub-array thereof). The array data are thus only copied once, through the COPY-SEQ. Sorry, I think I conflated a statement in your original and gugamilare's...

Something like this: (defun copy-array (a) (do ((b (make-array (array-dimensions a) :element-type (array-element-type a))) (n 0 (1+ n))) ((>= n (array-total-size a)) b) (setf (row-major-aref b n) (row-major-aref a n)))) Avoids the double copy you are making. Also note the existence of #'array-total-...

So nobody does these things, right? I thought about your quiz question over coffee. I've never dealt with XML in lisp before, or web interfaces so I thought it might be fun to see how much is involved. Luckily people have thought about this sort of problem and come up with some neat programs. So, he...

VECTOR-PUSH-EXTEND is what you want but array must be adjustable. http://www.lispworks.com/documentation/HyperSpec/Body/f_vec_ps.htm Arrays are continuous blocks of memory I really doubt you will gain much if at all by using simple array especially in accesing elements. Maybe it would be better if ...

Because of the support for complex numbers, this is pretty simply expressed in common lisp. I've made it a little more flexible with optional height/width arguments but otherwise left along. A clear improvement would be add a look up table into a list of characters ordered by "brightness"....