Allow sequential iterators in JSON external interface. #23
Description
Right now QualityBisectionIterator is the only allowed time stepping model in the FDM. We have code for a sequential iterator which allows arbitrary time stepping functions via anonymous functions. Is there any way to expose that consistently in the JSON external interface? Possibly via str2func or similar? This should be possible. The biggest difficulty is error-checking the user input before we get to the point where the function is needed.