function x = Func(typ, n, p)
%
% Func - a class for functors.
%
% A functor is an object that behaves like a function. Cantera
% defines a set of functors to use to create arbitrary functions to
% specify things like heat fluxes, piston speeds, etc., in reactor
% network simulations. Of course, they can be used for other things
% too.
%
% The main feature of a functor class is that it overloads the '()'
% operator to evaluate the function. For example, suppose object
% 'f' is a functor that evaluates the polynomial '2x^2 - 3x +
% 1'. Then writing 'f(2)' would cause the method that evaluates the
% function to be invoked, and would pass it the argument '2'. The
% return value would of course be 3.
%
% The types of functors you can create in Cantera are these:
% 1. A polynomial
% 2. A Fourier series
% 3. A sum of Arrhenius terms
% 4. A Gaussian.
% You can also create composite functors by adding, multiplying, or
% dividing these basic functors, or other composite functors.
%
% Note: this MATLAB class shadows the underlying C++ Cantera class
% "Func1". See the Cantera C++ documentation for more details.
%
if ~isa(typ, 'char')
    error('Function type must be a string')
end

x.f1 = 0;
x.f2 = 0;
x.coeffs = 0;

itype = -1;
if strcmp(typ, 'polynomial')
    itype = 2;
elseif strcmp(typ,'fourier')
    itype = 1;
elseif strcmp(typ,'arrhenius')
    itype = 3;
elseif strcmp(typ,'gaussian')
    itype = 4;
end

if itype > 0
    x.coeffs = p;
    x.index = funcmethods(0,itype,n,p);
elseif strcmp(typ,'periodic')
    itype = 50;
    x.f1 = n;
    x.coeffs = p;
    x.index = funcmethods(0,itype,n.index,p);
else
    if strcmp(typ,'sum')
        itype = 20;
    elseif strcmp(typ,'diff')
        itype = 25;
    elseif strcmp(typ,'prod')
        itype = 30;
    elseif strcmp(typ,'ratio')
        itype = 40;
    elseif strcmp(typ,'composite')
        itype = 60;
    end
    x.f1 = n;
    x.f2 = p;
    x.index = funcmethods(0,itype,n.index,p.index);
end

x.typ = typ;
x = class(x,'Func');