;;;;; Gambit v4.8.8

> (sqrt -inf.0+1.0i)
0.+inf.0i
> (sqrt -inf.0-1.0i)
0.-inf.0i
> 

;;;;; Chez Scheme Version 9.5.1

> (sqrt -inf.0+1.0i)
0.0+inf.0i
> (sqrt -inf.0-1.0i)
0.0-inf.0i
> 

;;;;; GNU Guile 2.2.3

scheme@(guile-user)> (sqrt -inf.0+1.0i)
$1 = 0.0+inf.0i
scheme@(guile-user)> (sqrt -inf.0-1.0i)
$2 = 0.0-inf.0i

;;;; This is SBCL 1.4.5.debian, an implementation of ANSI Common Lisp.

* (sqrt #C( #.SB-EXT:DOUBLE-FLOAT-NEGATIVE-INFINITY 1.0))
#C(0.0d0 #.SB-EXT:DOUBLE-FLOAT-POSITIVE-INFINITY)
* (sqrt #C( #.SB-EXT:DOUBLE-FLOAT-NEGATIVE-INFINITY -1.0))
#C(0.0d0 #.SB-EXT:DOUBLE-FLOAT-NEGATIVE-INFINITY)