On Mon, 20 Jun 2022, Raul Miller wrote:
"Language change: Scatter-amend support: x m} y changed when m is a numeric
array of rank>1. In that case, each 1-cell of m is the index list of a cell
of y that is replaced by the corresponding cell of x. This is an
incompatible change with J8.07 and earlier, but is compatible with previous
J9.01 betas."
I think, in retrospect, this should have been:
"Language change: Scatter-amend support: x m} y changed when m is a numeric
array of rank>1. In that case, each 1-cell of m is the index list of a frame
of y that is replaced by the corresponding frame of x. ..."
Oh, wow ...
I am not sure how to feel about this. Mainly, I am not sure what the
difference is between x m}y and (for high-ranked numeric m) x (<"1 m)} y. I
am also not sure what the difference is between your proposed semantics and
the existing ones.
I would still like to know what people think about making certain empty amends
legal, in the manner previously described.
Hmm... suffix shape alignment was the APL approach. J used to use prefix
shape alignment.
As far as I know, no apl used suffix rules for conformability. Two arrays of
like shape were conformable, and a scalar is conformable with anything; but no
two arrays are conformable aside from that. An early version of j did use
suffix conformability, and then switched.
-E
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