Hi Gabriel, > As an illustration, take the package ToolsForSign. It contains the > following definition for `sign'. > > if R has RetractableTo Fraction Integer then > sign r == > (u := retractIfCan(r)@Union(Fraction Integer, "failed")) > case Fraction(Integer) => sign(u::Fraction Integer) > nonQsign r > > else > if R has RetractableTo Integer then > sign r == > (u := retractIfCan(r)@Union(Integer, "failed")) > case "failed" => "failed" > sign(u::Integer) > > -- ... > > This the usual form of dealing with retractIfCan(), and I think it > looks gastly (well, my opinion). > And what is the nonQsign call ? I don't understand where this function is defined.
This category ToolsForSign avoids to recode this sign function in all domains. Am I right ? And suppose there is a better sign function in this domain. The definition of this function sign remains inside this domain. Must we suppress the declaration of the category ToolsForSign in this domain ? Or [EMAIL PROTECTED] overload [EMAIL PROTECTED] May we remplace nonQsign by [EMAIL PROTECTED] ? An other case where such domain may be useful : In all polynomial domains we often test if the polynom is constant (in R) or integer or monic. May be possible to have a category with functions which detect any p*a+q*b where p and q are integer for all polynomial domains. By example expand in expressions must operate over sin (3*a+2*b) and the 2 and 3 coefficients don't depend of the domain polynomial. Today axiom code uses only Polynomial domain and it's impossible to adapt expression to DistributedPolynomial for this reason (and others) And, last question, is there a such way to get in Expression the %i=sqrt(-1) : or does the code remain : if R has imaginary : R -> R then use innerI := imaginary()::Expression R else use innerI := sqrt(-1::R) rewrite rules for exp (an i * a) = cos (a) + thisI * sin (a) François ------------------------------------------------------------------------------ SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. The future of the web can't happen without you. Join us at MIX09 to help pave the way to the Next Web now. Learn more and register at http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ _______________________________________________ open-axiom-devel mailing list open-axiom-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/open-axiom-devel
