docs: add missing subscripts in sign definition

PR-URL: #844 Reviewed-by: Athan Reines <kgryte@gmail.com> Reviewed-by: Oleksandr Pavlyk <oleksandr.pavlyk@intel.com>

Author: mdhaber

src/array_api_stubs/_2022_12/elementwise_functions.py

@@ -2065,7 +2065,7 @@ def sign(x: array, /) -> array:
  .. math::
  \operatorname{sign}(x_i) = \begin{cases}
  0 & \textrm{if } x_i = 0 \\
- \frac{x}{|x|} & \textrm{otherwise}
+ \frac{x_i}{|x_i|} & \textrm{otherwise}
  \end{cases}
 
  where :math:`|x_i|` is the absolute value of :math:`x_i`.

src/array_api_stubs/_2023_12/elementwise_functions.py

@@ -2335,7 +2335,7 @@ def sign(x: array, /) -> array:
  .. math::
  \operatorname{sign}(x_i) = \begin{cases}
  0 & \textrm{if } x_i = 0 \\
- \frac{x}{|x|} & \textrm{otherwise}
+ \frac{x_i}{|x_i|} & \textrm{otherwise}
  \end{cases}
 
  where :math:`|x_i|` is the absolute value of :math:`x_i`.

src/array_api_stubs/_draft/elementwise_functions.py

@@ -2389,7 +2389,7 @@ def sign(x: array, /) -> array:
  .. math::
  \operatorname{sign}(x_i) = \begin{cases}
  0 & \textrm{if } x_i = 0 \\
- \frac{x}{|x|} & \textrm{otherwise}
+ \frac{x_i}{|x_i|} & \textrm{otherwise}
  \end{cases}
 
  where :math:`|x_i|` is the absolute value of :math:`x_i`.