Improve tests and fix error with recent Java

When moving to Java 17 some of the tests started failing.
It turns out it was because `Math/abs` was being used instead of `abs`
in the Clojure branch of `same.platform/bit-diff-double` and `bit-diff-float`.
For large differences this would overflow, so `(bit-diff-double 1.0 2.0)` would
return 0 instead of a large number.

Author: emlyn

src/same/platform.cljc

@@ -77,8 +77,8 @@
 (defn bit-diff-double
   "Difference between two doubles in ULPs (i.e. number of representable numbers between them + 1)."
   [f1 f2]
-  #?(:clj (Math/abs ^long (- (Double/doubleToLongBits f1)
-                             (Double/doubleToLongBits f2)))
+  #?(:clj (abs (- (Double/doubleToLongBits f1)
+                  (Double/doubleToLongBits f2)))
      :cljs (let [buf (js/ArrayBuffer. 16)
                  dv  (js/DataView. buf)]
              (.setFloat64 dv 0 (double f1))
@@ -90,8 +90,8 @@
 (defn bit-diff-float
   "Difference between two floats in ULPs (i.e. number of representable numbers between them + 1)."
   [f1 f2]
-  #?(:clj (Math/abs ^long (- (Float/floatToIntBits f1)
-                             (Float/floatToIntBits f2)))
+  #?(:clj (abs ^long (- (Float/floatToIntBits f1)
+                        (Float/floatToIntBits f2)))
      :cljs (let [buf (js/ArrayBuffer. 8)
                  dv  (js/DataView. buf)]
              (.setFloat32 dv 0 (float f1))

test/same/platform_test.cljc

@@ -45,5 +45,23 @@
   (is (p/nan? (p/ulp nan))))
 
 (deftest bit-diff-double-test
+  (is (zero? (p/bit-diff-double 1.0 1.0)))
   (is (= 1 (p/bit-diff-double 1.0 1.0000000000000002)))
-  (is (= 1 (p/bit-diff-double 1.0000000000000002 1.0))))
+  (is (= 1 (p/bit-diff-double 1.0000000000000002 1.0)))
+  (is (= 0x8000000000000 (p/bit-diff-double 1.0 1.5)))
+  (is (= 0x8000000000000 (p/bit-diff-double 1.5 1.0)))
+  (is (= 0x10000000000000 (p/bit-diff-double 1.0 2.0)))
+  (is (= 0x10000000000000 (p/bit-diff-double 2.0 1.0)))
+  (is (= 0x100000000000000 (p/bit-diff-double 1.0 65536.0)))
+  (is (= 0x100000000000000 (p/bit-diff-double 65536.0 1.0))))
+
+(deftest bit-diff-float-test
+  (is (zero? (p/bit-diff-float 1.0 1.0)))
+  (is (= 1 (p/bit-diff-float 1.0 1.0000001)))
+  (is (= 1 (p/bit-diff-float 1.0000001 1.0)))
+  (is (= 0x400000 (p/bit-diff-float 1.0 1.5)))
+  (is (= 0x400000 (p/bit-diff-float 1.5 1.0)))
+  (is (= 0x800000 (p/bit-diff-float 1.0 2.0)))
+  (is (= 0x800000 (p/bit-diff-float 2.0 1.0)))
+  (is (= 0x8000000 (p/bit-diff-float 1.0 65536.0)))
+  (is (= 0x8000000 (p/bit-diff-float 65536.0 1.0))))