[Mono-dev] Porting System.Numerics from referencesource, approaches for copying code?

Wed Dec 3 16:13:18 UTC 2014

To make this 100% clear: .NET implements locale aware number formatting in the VM, e.g. for format specifiers like 'e' (exponential) or 'f' (fixed-point)  it calls into the VM for formatting.
We don't have this in Mono atm., so the only way is to restrict it to the invariant format specifiers (which doesn't hurt existing Mono users, since it didn't work before too).
-- Alex

From: alex.koeplinger at outlook.com
To: miguel at xamarin.com
Date: Wed, 3 Dec 2014 17:01:42 +0100
CC: mono-devel-list at lists.ximian.com
Subject: Re: [Mono-dev] Porting System.Numerics from referencesource, approaches for copying code?

Hey,
we need to ensure we only continue for the format specifiers used in decimalFmt. Any other format specifier (i.e. culture-specific ones) would result in a call into unmanaged code later on (https://github.com/akoeplinger/referencesource/blob/mono/System.Numerics/System/Numerics/BigNumber.cs#L611-L634) which we of course don't have implemented.

Note that it only throws an exception when decimalFmt == false, i.e. when any of the culture-specific specifiers was used (which is *not* a common code path). This is exactly what the current Mono code also does: https://github.com/mono/mono/blob/f8a517624de3fdfc070d2f0660fce1b62d41bc4c/mcs/class/System.Numerics/System.Numerics/BigInteger.cs#L1470

-- Alex

From: miguel at xamarin.com
Date: Wed, 3 Dec 2014 10:52:04 -0500
Subject: Re: [Mono-dev] Porting System.Numerics from referencesource, approaches for copying code?
To: alex.koeplinger at outlook.com
CC: mono-devel-list at lists.ximian.com

Hello Alex,
I am not sure I am understanding this.
This looks like we are choosing to not bring features that we are missing?   Why would we want to do that?
Miguel
On Wed, Dec 3, 2014 at 10:33 AM, Alexander Köplinger <alex.koeplinger at outlook.com> wrote:

Mono today also only supports the format specifiers used in decimalFmt: https://github.com/mono/mono/blob/f8a517624de3fdfc070d2f0660fce1b62d41bc4c/mcs/class/System.Numerics/System.Numerics/BigInteger.cs#L1458-L1471

So using this #if for Mono is the correct way to go.

(reposted, seems like the mailing list ate my previous mail) 

-- Alex

From: miguel at xamarin.com
Date: Sat, 29 Nov 2014 12:06:20 -0500
Subject: Re: [Mono-dev] Porting System.Numerics from referencesource, approaches for copying code?
To: alex.koeplinger at outlook.com
CC: mono-devel-list at lists.ximian.com

Can you explain the rationale for the #if used with the same SILVERLIGHT setting?
It seems like it limits the code.
On Sat, Nov 29, 2014 at 12:03 PM, Alexander Köplinger <alex.koeplinger at outlook.com> wrote:

Yeah, that was what I was doing.

I created these PRs:
https://github.com/mono/referencesource/pull/1
https://github.com/mono/mono/pull/1433 

-- Alex

From: miguel at xamarin.com
Date: Sat, 29 Nov 2014 11:23:01 -0500
Subject: Re: [Mono-dev] Porting System.Numerics from referencesource, approaches for copying code?
To: alex.koeplinger at outlook.com
CC: mono-devel-list at lists.ximian.com

I just realized it might not have been 100% clear what I think we should do.
We would in this case replace the references to our mono/mcs/class/XX/*/*cs source files, with the "../../external/referencesource/..." files, and then alter the original referencesource file with the #if statements.
We have done that already in a couple of places.
(More to come, last night we got XML working, but needs some work)
On Sat, Nov 29, 2014 at 11:21 AM, Miguel de Icaza <miguel at xamarin.com> wrote:
Thanks Alex.
I do not think that we will have a strict rule for when to copy and when to reference.  
There are scenarios where we will want to keep a lot of the code in one of our files, and pull code from the referencesource.   At that point, we will have to determine whether the use of #ifdefs or partial classes is a better long-term maintenance approach than copying the source.
In this particular case, I feel that we can modify the reference source, and add the #if MONO around it.
The reason is that the changes are pretty straight forward, it is mostly about disabling code, and not about picking some specific bits of code and putting them on our tree.   So an #if would be nice, since we can do a few things (a) we can later find out what code is being disabled by the port (looking at work we can do in the future to import new versions, or contribute back to .NET) and (b) the changes are minimal right now.
Miguel
On Sat, Nov 29, 2014 at 10:59 AM, Alexander Köplinger <alex.koeplinger at outlook.com> wrote:

Here's the diff between my trimmed version and the original: http://www.mergely.com/9E70e5Ls/

Hmm, I actually think that most of the removed methods don't matter (as they aren't called anyway). I just wanted to make the file only contain the code that is necessary.
The only "real" changes I had to make where accesses to internal fields in NumberFormatInfo, I just replaced them with accesses to the public properties that read them.

Maybe it makes more sense to correct those accesses directly in the referencesource, so we can reference it from there?
As a general guidance, when should we copy something to the Mono tree vs. editing referencesource? And if we copy, should we keep unneeded methods or remove them? 

-- Alex

From: miguel at xamarin.com
Date: Sat, 29 Nov 2014 10:40:10 -0500
Subject: Re: [Mono-dev] Porting System.Numerics from referencesource, approaches for copying code?
To: alex.koeplinger at outlook.com
CC: mono-devel-list at lists.ximian.com

Hey Alex,
In general, the approach works.
I am curious as to what is that you had to remove, and why.   Can you describe the needed changes?   (I saw the diff, but it is hard to tell what happened with it).
I thought that Numerics was pretty much standalone.
On Sat, Nov 29, 2014 at 10:32 AM, Alexander Köplinger <alex.koeplinger at outlook.com> wrote:

Hey, I've been trying to port System.Numerics (BigInteger, Complex classes) from referencesource to see and feel what the process looks like.
It mostly went fine, but there was one file (number.cs) I couldn't reference directly from the submodule and had to copy to the assembly folder in the Mono tree.

I had to remove a bunch of code from that file to trim it down to only what is needed for System.Numerics to compile (all the tests pass now as well).
Question: is this a valid approach or is there something better? Note that ifdefing the file wasn't feasible as it originally sits inside corlib and has many other unrelated methods in it.

Here's the commit with the WIP: https://github.com/akoeplinger/mono/commit/d7c461155a975a35f76b79ebcc3fe33407bd5dce

-- Alex

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