It sort of helps in the sense that the hint about specifying the types is useful. I could not apply the solution directly because it lead to another very surprising (to me) quirk of FriCAS: lack of a basic form of referential transparency between variables and literals. Namely if you assign a literal to a variable and later in code use a variable, the result may be different than if you had used the literal instead. For example:
Let's assign an expression to a variable: BS := ((S*erf(((2*log((S/K))+T*s^2+2*T*r)/(2*s*sqrt(2)*sqrt(T))))-K*%e^((-T*r))*erf(((2*log((S/K))-T*s^2+2*T*r)/(2*s*sqrt(2)*sqrt(T))))-K*%e^((-T*r))+S)/2) define an abbreviation for DoubleFloat F:=DoubleFloat Now define a function using the literal C0(S:F,r:F,T:F,K:F,s:F):F == ((S*erf(((2*log((S/K))+T*s^2+2*T*r)/(2*s*sqrt(2)*sqrt(T))))-K*%e^((-T*r))*erf(((2*log((S/K))-T*s^2+2*T*r)/(2*s*sqrt(2)*sqrt(T))))-K*%e^((-T*r))+S)/2) And another one using the variable which stores that literal C1(S:F,r:F,T:F,K:F,s:F):F == BS Now the first function can be evaluated C0(10.0,0.05,0.8,11.0,0.05) 0.023903294619544546 But the second cannot C1(10.0,0.05,0.8,11.0,0.05) Cannot convert the value from type Expression(Integer) to DoubleFloat . It seems the only way to create a function when the expression is stored in a variable is to first declare the function C2:(F,F,F,F,F) -> F Then use the function operation to create the function from the expression function(BS,'C2,['S,'r,'T,'K,'s]) Then such function can be evaluated C2(10.0,0.05,0.8,11.0,0.05) 0.023903294619544546 On Saturday, November 10, 2018 at 12:07:44 PM UTC+1, Ralf Hemmecke wrote: > > Is there a way to force the evaluation of erf so that the function > > s+->C(11.0,s) can be plotted? > > Does the following help? > > The idea is that you specify the type so that the result is not > Expression(Float) (and must later be converted to (Double)Float, but > rather an element of DoubleFloat. > > Ralf > > F ==> DoubleFloat > > C0(S:F,r:F,T:F, > K:F,s:F):F==((S*erf(((2*log((S/K))+T*s^2+2*T*r)/(2*s*sqrt(2)*sqrt(T))))-K*%e^((-T*r))*erf(((2*log((S/K))-T*s^2+2*T*r)/(2*s*sqrt(2)*sqrt(T))))-K*%e^((-T*r))+S)/2) > > > > C(K:F, s:F):F==C0(10.0, 0.05, 0.8, K, s) > > CC(s:F):F==C(11.0, s) > > draw(CC, 2.0..3.0) > -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To unsubscribe from this group and stop receiving emails from it, send an email to fricas-devel+unsubscr...@googlegroups.com. To post to this group, send email to fricas-devel@googlegroups.com. Visit this group at https://groups.google.com/group/fricas-devel. For more options, visit https://groups.google.com/d/optout.
