ENH: add dtype kwarg to fft.{fftfreq, rfftfreq}

Author: ev-br

array_api_strict/_fft.py

@@ -251,26 +251,52 @@ def ihfft(
     return res
 
 @requires_extension('fft')
-def fftfreq(n: int, /, *, d: float = 1.0, device: Optional[Device] = None) -> Array:
+def fftfreq(
+    n: int,
+    /,
+    *,
+    d: float = 1.0,
+    dtype: Optional[dtype] = None,
+    device: Optional[Device] = None
+) -> Array:
     """
     Array API compatible wrapper for :py:func:`np.fft.fftfreq <numpy.fft.fftfreq>`.
 
     See its docstring for more information.
     """
     if device is not None and device not in ALL_DEVICES:
         raise ValueError(f"Unsupported device {device!r}")
-    return Array._new(np.fft.fftfreq(n, d=d), device=device)
+    if dtype and not dtype in _real_floating_dtypes:
+        raise ValueError(f"`dtype` must be a real floating-point type. Got {dtype=}.")
+
+    np_result = np.fft.fftfreq(n, d=d)
+    if dtype:
+        np_result = np_result.astype(dtype._np_dtype)
+    return Array._new(np_result, device=device)
 
 @requires_extension('fft')
-def rfftfreq(n: int, /, *, d: float = 1.0, device: Optional[Device] = None) -> Array:
+def rfftfreq(
+    n: int,
+    /,
+    *,
+    d: float = 1.0,
+    dtype: Optional[dtype] = None,
+    device: Optional[Device] = None
+) -> Array:
     """
     Array API compatible wrapper for :py:func:`np.fft.rfftfreq <numpy.fft.rfftfreq>`.
 
     See its docstring for more information.
     """
     if device is not None and device not in ALL_DEVICES:
         raise ValueError(f"Unsupported device {device!r}")
-    return Array._new(np.fft.rfftfreq(n, d=d), device=device)
+    if dtype and not dtype in _real_floating_dtypes:
+        raise ValueError(f"`dtype` must be a real floating-point type. Got {dtype=}.")
+
+    np_result = np.fft.rfftfreq(n, d=d)
+    if dtype:
+        np_result = np_result.astype(dtype._np_dtype)
+    return Array._new(np_result, device=device)
 
 @requires_extension('fft')
 def fftshift(x: Array, /, *, axes: Union[int, Sequence[int]] = None) -> Array: