Ironruby core - May 2011 - How to iterate through a C# IEnumerable from IronRuby?

Apologies if this is a basic Ruby question. I have a C# method:

public class Myro {
  ...
  public static IEnumerator getPixels(Picture picture) {
    for (int x=0; x < picture.width; x++) {
      for (int y=0; y < picture.height; y++) {
          yield return picture.getPixel(x, y);
      }
    }
  }
}

I can call this fine in IronPython:

for pixel in getPixels(pic):
    r, g, b = getRGB(pixel)
    gray = (r + g + b)/3
    setRGB(pixel, gray, gray, gray)

But I don''t see how to call this from IronRuby:

Myro::getPixels(pic) do |pixel|
    r, g, b = Myro::getRGB pixel
    gray = (r + g + b)/3
    Myro::setRGB(pixel, gray, gray, gray)
end

All I get back is Myro+<getPixels>c__Iterator0.

What do I need to do to actually get each pixel in IronRuby and
process it? Do I need an extension method, perhaps called "each"? If
so, can someone point me to some code?

Thanks in advance for any help,

-Doug

Doug,

If you change the return type of getPixels to IEnumerable, then this works:

    Myro::getPixels(pic).each do |pixel|
        ...
    end

And arguably it should be IEnumerable rather than IEnumerator, as an
IEnumerable.GetEnumerator() gives you an IEnumerator.

Your code example passes a closure to the getPixels method, which just
gets ignored (all Ruby methods syntactically accept a block/closure,
and they can choose to use it), and returns the IEnumerator.

IronRuby today doesn''t support mapping Ruby''s Enumerable
module to
IEnumerator objects, since it''s kind awkward to return an IEnumerator
rather than an IEnumerable from a public API, but since IronPython
sets a precedence for supporting it we should look into it. Opened
http://ironruby.codeplex.com/workitem/6154.

~Jimmy



On Tue, May 24, 2011 at 8:41 AM, Doug Blank <doug.blank at gmail.com>
wrote:
> Apologies if this is a basic Ruby question. I have a C# method:
>
> public class Myro {
> ?...
> ?public static IEnumerator getPixels(Picture picture) {
> ? ?for (int x=0; x < picture.width; x++) {
> ? ? ?for (int y=0; y < picture.height; y++) {
> ? ? ? ? ?yield return picture.getPixel(x, y);
> ? ? ?}
> ? ?}
> ?}
> }
>
> I can call this fine in IronPython:
>
> for pixel in getPixels(pic):
> ? ?r, g, b = getRGB(pixel)
> ? ?gray = (r + g + b)/3
> ? ?setRGB(pixel, gray, gray, gray)
>
> But I don''t see how to call this from IronRuby:
>
> Myro::getPixels(pic) do |pixel|
> ? ?r, g, b = Myro::getRGB pixel
> ? ?gray = (r + g + b)/3
> ? ?Myro::setRGB(pixel, gray, gray, gray)
> end
>
> All I get back is Myro+<getPixels>c__Iterator0.
>
> What do I need to do to actually get each pixel in IronRuby and
> process it? Do I need an extension method, perhaps called "each"?
If
> so, can someone point me to some code?
>
> Thanks in advance for any help,
>
> -Doug
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