[Marabou] Custom format for negative reals.

src/printers/marabou.ml

@@ -21,7 +21,8 @@ let number_format =
     Why3.Number.hex_int_support = `Unsupported;
     Why3.Number.oct_int_support = `Unsupported;
     Why3.Number.bin_int_support = `Unsupported;
-    Why3.Number.negative_real_support = `Default;
+    Why3.Number.negative_real_support =
+      `Custom (fun fmt f -> Fmt.pf fmt "-%t" f);
     Why3.Number.dec_real_support = `Default;
     Why3.Number.hex_real_support = `Unsupported;
     Why3.Number.frac_real_support = `Unsupported (fun _ _ -> assert false);