`Sometimes you start working on a ticket thinking "this is just a few`

`hours of work" when it turns out to be a huge can of worms...`

`Coercion for multi-variate polynomials might fall in this category.`

`There are several strange things and bugs. The best example so far:`

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sage: R.<x,y> = QQ[] sage: QQ["y,x"](x) x sage: R.<x,y> = QQbar[] sage: QQbar["y,x"](x) y So depending on the base ring, you get different maps R[x,y] -> R[y,x]. In both cases, Sage considers this map a coercion.

`I would like to forget the current situation and simply start from`

`scratch thinking which maps should be coercions. I don't have a good`

`idea so far, I wonder if somebody else does.`

I'd like to say that the following should be coercions: R -> R[x,y] R[x] -> R[x,y] R[y] -> R[x,y] R[x][y] -> R[x,y] But not the following: R[x,y] -> R[x][y] R[x,y] -> R[y,x] R[x,y][z] -> R[x][y,z] -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.