Implement matrix multiplication operator (PEP 465)

[abalkin]

BPO	21176
Nosy	@jcea, @abalkin, @benjaminp, @njsmith
Files	mat-mult1.patch mat-mult2.patch mat-mult3.patch mat-mult4.patch mat-mult5.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/benjaminp'
closed_at = <Date 2014-04-10.03:56:05.754>
created_at = <Date 2014-04-08.02:51:34.953>
labels = ['interpreter-core', 'type-feature']
title = 'Implement matrix multiplication operator (PEP 465)'
updated_at = <Date 2014-06-12.00:57:19.493>
user = 'https://github.com/abalkin'

bugs.python.org fields:

activity = <Date 2014-06-12.00:57:19.493>
actor = 'jcea'
assignee = 'benjamin.peterson'
closed = True
closed_date = <Date 2014-04-10.03:56:05.754>
closer = 'python-dev'
components = ['Interpreter Core']
creation = <Date 2014-04-08.02:51:34.953>
creator = 'belopolsky'
dependencies = []
files = ['34754', '34755', '34756', '34758', '34762']
hgrepos = []
issue_num = 21176
keywords = ['patch']
message_count = 15.0
messages = ['215724', '215726', '215730', '215731', '215732', '215734', '215735', '215736', '215737', '215738', '215739', '215740', '215762', '215863', '215865']
nosy_count = 5.0
nosy_names = ['jcea', 'belopolsky', 'benjamin.peterson', 'njs', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue21176'
versions = ['Python 3.5']

[abalkin]

[Nathaniel Smith at numpy-discussion]

Guido just formally accepted PEP-465:
https://mail.python.org/pipermail/python-dev/2014-April/133819.html
http://legacy.python.org/dev/peps/pep-0465/#implementation-details

Yay.

The next step is to implement it, in CPython and in numpy. I have time
to advise on this, but not to do it myself, so, any volunteers? Ever
wanted to hack on the interpreter itself, with BDFL guarantee your
patch will be accepted (if correct)?

The todo list for CPython is here:
http://legacy.python.org/dev/peps/pep-0465/#implementation-details
There's one open question which is where the type slots should be
added. I'd just add them to PyNumberMethods and then if someone
objects during patch review it can be changed.

[benjaminp]

Here's a first patch. It works, but needs more tests (associativity, precedence, __rmatmul__, etc...) and also docs. I can work on that tomorrow.

[benjaminp]

Here are changes to the operator module...

[abalkin]

I've got to the point where I can do

>>> import ast
>>> ast.dump(ast.parse('a @ b'))
"Module(body=[Expr(value=BinOp(left=Name(id='a', ctx=Load()), op=MatMult(), right=Name(id='b', ctx=Load())))])"

I'll post a link to my bitbucket clone shortly.

[benjaminp]

Here is a nearly complete patch...

[abalkin]

Wow! That was quick. And I am still fighting with bitbucket. Maybe I should stop duplicating the effort at this point.

[benjaminp]

On Mon, Apr 7, 2014, at 22:09, Alexander Belopolsky wrote:

Alexander Belopolsky added the comment:

Wow! That was quick. And I am still fighting with bitbucket. Maybe I
should stop duplicating the effort at this point.

Sorry about that. I only saw the first message, where Nathaniel invites
an implementation. I didn't realize that was a direct quote from the
mailing list (not by you) and didn't notice you also assigned it to
yourself.

[abalkin]

Thanks for stepping in. From a quick look at your patch I don't see anything that I would do much differently.

I noticed some whitespace issues in Include/token.h:

-#define AT              49	
-#define RARROW          50
-#define ELLIPSIS        51
+#define AT              49
+#define ATEQUAL		50
+#define RARROW          51
+#define ELLIPSIS        52

(Are you sure you want to re-enumerate RARROW and ELLIPSIS? Why not just give ATEQUAL the value of 52?)

[abalkin]

+ .. versionadded:: 3.4

Are you planning to use the time machine? :-)

[benjaminp]

On Mon, Apr 7, 2014, at 22:23, Alexander Belopolsky wrote:

Alexander Belopolsky added the comment:

Thanks for stepping in. From a quick look at your patch I don't see
anything that I would do much differently.

I noticed some whitespace issues in Include/token.h:

-#define AT 49
-#define RARROW 50
-#define ELLIPSIS 51
+#define AT 49
+#define ATEQUAL 50
+#define RARROW 51
+#define ELLIPSIS 52

(Are you sure you want to re-enumerate RARROW and ELLIPSIS? Why not just
give ATEQUAL the value of 52?)

I thought it would be nicer if ATEQUAL was right after AT.

[benjaminp]

On Mon, Apr 7, 2014, at 22:25, Alexander Belopolsky wrote:

Alexander Belopolsky added the comment:

• .. versionadded:: 3.4

Are you planning to use the time machine? :-)

Good catch. :)

[benjaminp]

Here's my latest and greatest version. I'll finish up after some sleep.