The ODE system function f is referred by the string 'fct'. If we describe a method with second derivative, we can refer to f' by the string 'dfct'. The stepsize of the method is referred by the reserved variable name 'h'.
Checks are made for each expression introduced by the user. A Polish sequence is created for the right side of each iterative equation. The evaluation of this Polish sequence differs from the evaluation of the Polish sequences associated to problem equations in the following: in the last case, the variables are replaced by floating point numbers, and in the first case, the variables are replaced by n-dimensional vectors of floating point numbers (n being the ODE system dimension). The user must pay attention to the operands of the '*' and '/'. In almost all A-methods at least one operand of this arithmetic operation is scalar. Exception to this rule are the nonlinear methods.
EpODE permits an operation of '*' or '/' between two vectors: the multiplication/division is made on corresponding components;