handle signed zero in li(n)

Expander · Mar 6, 2024 · 51618d1 · 51618d1
1 parent e27eb5c
commit 51618d1
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Showing 3 changed files with 23 additions and 2 deletions.
diff --git a/src/li/cli.rs b/src/li/cli.rs
@@ -14,7 +14,7 @@ pub fn cli(n: i32, z: Complex<f64>) -> Complex<f64> {
         Complex::new(f64::NEG_INFINITY, 0.0)
     } else if z.im == 0.0 {
         if z.re <= 1.0 || n <= 0 {
-            Complex::new(z.re.li(n), 0.0)
+            Complex::new(z.re.li(n), z.im)
         } else { // rz > 1.0 && n > 0
             let l = z.re.ln();
             Complex::new(z.re.li(n), -std::f64::consts::PI*inv_fac(n - 1)*l.powi(n - 1))

diff --git a/src/li/rli.rs b/src/li/rli.rs
@@ -11,7 +11,7 @@ pub fn rli(n: i32, x: f64) -> f64 {
     let odd_sgn = |n| if is_even(n) { -1.0 } else { 1.0 };
 
     if x == 0.0 {
-        0.0
+        x
     } else if x == 1.0 {
         zeta(n)
     } else if x == -1.0 {

diff --git a/tests/li.rs b/tests/li.rs
@@ -63,3 +63,24 @@ fn test_values() {
     assert!(Complex::new(f64::NAN, f64::NAN).li(7).is_nan());
     assert!(Complex::new(f64::INFINITY, f64::INFINITY).li(7).is_infinite());
 }
+
+
+#[test]
+fn test_signed_zero() {
+    let pz64 = 0.0_f64;
+    let nz64 = -0.0_f64;
+
+    for n in (-100..100).into_iter() {
+        assert!(pz64.li(n).is_sign_positive());
+        assert!(nz64.li(n).is_sign_negative());
+
+        assert!(Complex::new(pz64, pz64).li(n).re.is_sign_positive());
+        assert!(Complex::new(pz64, pz64).li(n).im.is_sign_positive());
+        assert!(Complex::new(pz64, nz64).li(n).re.is_sign_positive());
+        assert!(Complex::new(pz64, nz64).li(n).im.is_sign_negative());
+        assert!(Complex::new(nz64, pz64).li(n).re.is_sign_negative());
+        assert!(Complex::new(nz64, pz64).li(n).im.is_sign_positive());
+        assert!(Complex::new(nz64, nz64).li(n).re.is_sign_negative());
+        assert!(Complex::new(nz64, nz64).li(n).im.is_sign_negative());
+    }
+}