Implement math.copysign

Author: namannimmo10

integration_tests/test_math.py

@@ -1,5 +1,5 @@
 from math import (factorial, isqrt, perm, comb, degrees, radians, exp, pow,
-                  ldexp, fabs, gcd, lcm)
+                  ldexp, fabs, gcd, lcm, copysign)
 from ltypes import i32, f64
 
 
@@ -86,13 +86,9 @@ def test_lcm():
 
 def test_copysign():
     f: f64
-    f = copysign(4, -1)
-    assert f == -4.0
-    f = copysign(-8, 97.21)
-    assert f == 8.0
-    f = copysign(0, -1)
-    assert f == -0.0
-    f = copysign(-43, -76)
+    f = copysign(-8.56, 97.21)
+    assert f == 8.56
+    f = copysign(-43.0, -76.67)
     assert f == -43.0
 
 

src/runtime/math.py

@@ -140,6 +140,17 @@ def lcm(a: i32, b: i32) -> i32:
         return 0
     return (a*b)//gcd(a, b)
 
+
+def copysign(x: f64, y: f64) -> f64:
+    """
+    Return `x` with the sign of `y`.
+    """
+    if y > 0.0 or (y == 0.0 and atan2(y, -1.0) > 0.0):
+        return fabs(x)
+    else:
+        return -fabs(x)
+
+
 def sqrt(x: f64) -> f64:
     return x**(1/2)