problem with using external functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg91547] problem with using external functions*From*: Valery Yundin <yundin at ifh.de>*Date*: Wed, 27 Aug 2008 06:40:46 -0400 (EDT)

Dear MathGroup, I've a problem with using external functions defined in MathLink app. I guess the problem is in the evaluation order. I'm giving more details below. This is the function template: :Begin: :Function: my_xfxM :Pattern: xfxM[nset_Integer, x_Real, Q_] :Arguments: {nset, x, Q} :ArgumentTypes: {Integer, Real64, Real64} :ReturnType: Manual :End: The function body (the return value is list of doubles): void my_xfxM(const int nset, const double x, const double Q) { vector<double> result = LHAPDF::xfxM(nset, x, Q); double* c_result = &(*result.begin()); MLPutReal64List(stdlink, c_result, result.size()); } I'm defining another function in Mathematica: (it should multiply list of values returned by fucntion call by reversed list of another function call and drop first 7 elements. eg. if xfxM(1, x, 100.) returns {x1, ..., x14} the result should be: Plus@@{x8*y14,x9*y13,...,x14*y8}) myintegrand = Function[{x, y}, (Plus @@ (Drop[xfxM[1, x, 100.] Reverse[xfxM[1, y, 100.]], 7]))] Direct evaluation works well myintegrand[0.5, 0.3] But smth like this does not work: myintegrand[x, y] /. {x->0.5, y->0.3} And also when I try to integrate this function: NIntegrate[myintegrand[x, y], {x, 0.001, 1}, {y, 0.001, 1}, Method -> {"LocalAdaptive"}] The NIntegrate gives error message: Drop::drop: Cannot drop positions 1 through 7 in xfxM[1,x,100.] \ xfxM[100.,y,1]. >> NIntegrate::inum: "Integrand (7+xfxM[1,x,100.]\xfxM[100.,y,1])/(14000\ \x\y) is not numerical at {x,y} = {0.50048828125`,0.50048828125`}" How should I define my function to make this work? I think the problem is that Mathematica tries to evaluate function body with formal parameters (of "Symbol" type) not with just numerical values. -- With best regards, Valery Yundin.