Slice a Tensor and collapse singleton dimension.

Input:

• a Tensor
• and:
  • specific coordinates (varargs[int])
  • or a slice (cf. tutorial)

Returns:

• a value or a view of the Tensor corresponding to the slice Singleton dimension are collapsed

Usage: See the [] macro

Slice a Tensor, collapse singleton dimension, returning a mutable slice of the input

This can be useful, for example, when assigning a value into a chain of slice operations which are usually considered immutable even if the original tensor is mutable. For example, this lets you do:

var x = arange(12).reshape([4, 3])
let condition = [[true, false, true], [true, false, true]].toTensor
# The code `x[1..2, _][condition] = 1000` would fail with
# a `a slice of an immutable tensor cannot be assigned to` error
# Instead, using `at_mut` allows assignment to the slice
x.at_mut(1..2, _)[condition] = 1000

Input:

• a Tensor
• and:
  • specific coordinates (varargs[int])
  • or a slice (cf. tutorial)

Returns:

• a mutable value or view of the Tensor corresponding to the slice Singleton dimension are collapsed