I'm a little puzzled by the following and I didn't notice anything about this in: http://www-swiss.ai.mit.edu/~jaffer/r5rs_8.html#SEC51 (ceiling -.75) => -0.0 [negative zero?] (exact? 0) => #t [makes sense] (exact? -0) => #t [not only does negative zero exist, it's exact!?]