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homotopy-io / homotopy-webclient

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Cannot attach 3-cell to target. #127

Closed jordan-sawdy closed 3 years ago

jordan-sawdy commented 3 years ago

Here's my workspace. I'm pretty sure that clicking somewhere in the yellow line (the 'R' string) should attach the 'L snake' 3-cell, whiskering it with the zig zag on the right. It doesn't seem to want to do that, though. I might just be doing something wrong, but I feel like it should be able to do that. Thanks!

alexarice commented 3 years ago

Hi, the problem here is that you can not apply the L snake 3-cell as the target is at the same horizontal level as the zigzag on the right of the diagram. If you look in the next projection up it might be possible to see that these two look like they are on top of each other, which is why the cell cannot be applied. To get the diagram you want, you need to drag the left zigzag so that it is either completely below or above the right zigzag. Then you can apply the cell like this. After this you can go to the projection above and try to move stuff around to "fix" things.

alexarice commented 3 years ago

As a further explanation, applying L snake to the left part of the diagram shrinks this part of the diagram to a single point and then transforms that point to the identity. If this is at the same level as right zigzag, this operation would require the right zigzag to also contract to a single level at the same time, which cannot be done.

jordan-sawdy commented 3 years ago

Fantastic, thank you for the quick response and resolution!