The documentation for array-copy[!] states:

  Assumes that `array` is an array, `storage-class` is a storage class

  that can manipulate all the elements of `array` [...]

Here I assume "manipulate" means accept as a setter value,

which is what Chibi implements.  Thus it is never possible to

convert from an exact storage class to an inexact one, or vice

versa, even if the values will fit.  Converting between inexact

storages will always work, and converting between exact

storages will depend on the actual values.

It's actually extremely common and useful to allow exactness

conversions, e.g. as done by tensorflow tf.cast or pytorch

Tensor.to().  The former throws an error if the values don't fit,

though the latter is woefully underdocumented and seems to

coerce the values arbitrarily.

We could consider an all-in-one conversion with rounding

and bounding rules, but it's sufficient to have a procedure

that will just perform exactness conversions as needed and

leave ensuring the values fit to the programmer.

Depending on how much ambiguity people read into

"manipulate" it may be too late to clarify array-copy to

support this though.

--

Alex