Fix issue #20 with saturating_abs macros [to use std fns once stablized]

src/eq.rs

@@ -99,7 +99,7 @@ impl ApproxEq for f32 {
         {
             // Perform ulps comparion last
             let diff: i32 = self.ulps(&other);
-            diff.abs() <= margin.ulps
+            saturating_abs_i32!(diff) <= margin.ulps
         }
     }
 }
@@ -227,7 +227,7 @@ impl ApproxEq for f64 {
         {
             // Perform ulps comparion last
             let diff: i64 = self.ulps(&other);
-            diff.abs() <= margin.ulps
+            saturating_abs_i64!(diff) <= margin.ulps
         }
     }
 }
@@ -277,3 +277,7 @@ fn f64_approx_eq_test6() {
     println!("Ulps Difference: {}",x.ulps(&y));
     assert!(x.approx_eq(y, (0.0, 3)) == true);
 }
+#[test]
+fn f64_code_triggering_issue_20() {
+    assert_eq!((-25.0f64).approx_eq(25.0, (0.00390625, 1)), false);
+}

src/macros.rs

@@ -20,6 +20,32 @@ macro_rules! approx_eq {
     };
 }
 
+// Until saturating_abs() comes out of nightly, we have to code it ourselves.
+macro_rules! saturating_abs_i32 {
+    ($val:expr) => {
+        if $val.is_negative() {
+            match $val.checked_neg() {
+                Some(v) => v,
+                None => std::i32::MAX
+            }
+        } else {
+            $val
+        }
+    };
+}
+macro_rules! saturating_abs_i64 {
+    ($val:expr) => {
+        if $val.is_negative() {
+            match $val.checked_neg() {
+                Some(v) => v,
+                None => std::i64::MAX
+            }
+        } else {
+            $val
+        }
+    };
+}
+
 #[test]
 fn test_macro() {
     let a: f32 = 0.15 + 0.15 + 0.15;