Apply suggestion to bilby/core/utils.py

bilby/core/utils.py

@@ -1005,6 +1005,26 @@ def decode_astropy_quantity(dct):
 
 
 def reflect(u):
+    """
+    Iteratively reflect a number until it is contained in [0, 1].
+
+    This is for priors with a reflective boundary condition, all numbers in the set `u = 2n +/- x` should be mapped to x.
+
+    For the `+` case we just take `u % 1`.
+    For the `-` case we take `1 - (u % 1)`.
+
+    E.g., -0.9, 1.1, and 2.9 should all map to 0.9.
+
+    Parameters
+    ----------
+    u: array-like
+        The array of points to map to the unit cube
+
+    Returns
+    -------
+    u: array-like
+       The input array, modified in place.
+    """
     idxs_even = np.mod(u, 2) < 1
     u[idxs_even] = np.mod(u[idxs_even], 1)
     u[~idxs_even] = 1 - np.mod(u[~idxs_even], 1)