These are the R6RS examples involving -0.0 (already accounted for verbally in the "Implementation extensions" section of R7RS):
(zero? -0.0) => #t ; -0.0 is a Scheme zero (+ 0.0 0.0) => 0.0 ; Sum is -0.0 only if all arguments are -0.0 (+ 0.0 -0.0) => 0.0 (+ -0.0 0.0) => 0.0 (+ -0.0 -0.0) => -0.0 (- 0.0) => -0.0 ; Negation flips the sign of zero (- -0.0) => 0.0 (- 0.0 -0.0) => 0.0 ; Negate all arguments but the last and then add (- -0.0 0.0) => -0.0 (- 0.0 0.0) => 0.0 (- -0.0 -0.0) => 0.0 (log -1.0+0.0i) => 0.0+3.141592653589793i ; approximately (log -1.0-0.0i) => 0.0-3.141592653589793i ; approximately (angle -1.0+0.0i) => 3.141592653589793 ; approximately (angle -1.0-0.0i) => -3.141592653589793 ; approximately