List addition and multiplication not working about micropython HOT 8 CLOSED

Yep, not yet implemented! This should be easy to do, just add the relevant functionality to py/objlist.c, in the function list_binary_op. Maybe someone wants to have a go at it? :)

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I don't know if I will be able to find the time but I'll take a look. The related extend() method for lists is also missing but it's the same code.

While we're at it, string multiplication is also missing.

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Thanks for that Chipaca. I had been tinkering on this this evening too but it seem that you got there first. Since you are already working on this shall I stop on the RT_BINARY_OP_INPLACE_ADD, RT_BINARY_OP_MULTIPLY and RT_BINARY_OP_INPLACE_MULTIPLY too?

I was also implementing list.extend(), which is similar to RT_BINARY_OP_INPLACE_ADD save that it needs to work with any iterable object. This lead me down three different ratholes which it would be helpful if Damien could clarify. These are (in no particular order):

1. Can we count on the garbage collector to clear up heap objects allocated in the course of executing C code (such as iterator for other objects) without any hints being given? I'm used to coding for CPython so documenting the differences here would be helpful.
2. What is the correct style for iterating over the items in an utterable object from within the C code? If the answer to the question above is 'yes' then I presume I just call the getiter function in the object structure and have at it.
3. What is the correct style for throwing Python exceptions (such as type errors) from within C code? The binary_op table lets me just return NULL but if I am in a function like list.extend() and need to return a meaningful error I need to do some more.

While I can probably glean the answers to these from the rest of the code but it would help people getting started if we could have the answers to these written down somewhere.

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As that was my first patch to the project I was waiting for feedback before moving on. So don't stop if you're doing the other ones.

Do, however, consider this: list.extend is exactly the same as list.__iadd__. That is, in CPython 3.3:

>>> a = []
>>> a += range(10)
>>> a
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

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Aha. I had not noticed that:

l = [1,2,3]
l = l + 'foo'

behaves completely differently to:

l = [1,2,3]
l += 'foo'

Learn something new every day!

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Now we have #42 & #43 . Bottom line: we should somehow sync who's going to/working on something. The process I propose is you post a ticket (if one doesn't exist), and also comment(s) on related ticket where you know it was discussed. Example: #46.

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Yeap.

On Fri, Jan 3, 2014 at 11:06 AM, Paul Sokolovsky
[email protected]:

Now we have #42 #42 & #43#43. Bottom line: we should somehow sync who's going to/working on something.
The process I propose is you post a ticket (if one doesn't exist), and also
comment(s) on related ticket where you know it was discussed. Example: #46#46
.

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John Lenton ([email protected]) ::: http://chipaca.com

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Both list addition and multiplication is implemented now, with unit tests.

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