Dear William, On May 22, 4:09 pm, "William Stein" <[EMAIL PROTECTED]> wrote: > I disagree. There is a canonical coercion to the symbolic ring.
It seems that i need to learn more about canonical coercion. I thought that a coercion map goes between two parent structures, according to http://modular.math.washington.edu/sage/doc/html/prog/node17.html But the strings do not form a parent structure (or at least, 'x'.parent() is not defined). In fact there is no coercion around: sage: x.parent()._coerce_('x') Traceback ... <type 'exceptions.TypeError'>: cannot coerce type '<type 'str'>' into a SymbolicExpression. Consequently, we have sage: x == 'x***2' False According to http://modular.math.washington.edu/sage/doc/html/prog/node17.html, var('x')=='x' should return False as well, since there is no coercion between strings and SymbolicExpression. So, in what sense is var('x')=='x' involving a canonical coercion map? Is there a definition of "coercion map" and of "canonical", except the page http://modular.math.washington.edu/sage/doc/html/prog/node17.html? Yours Simon --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
