Forgive me if I am putting this in the wrong place, but this is my first post here. The question that I have is directed to the more experienced researchers than I am, I guess. In the Hamiltonian formulation of QFTs we write everything in terms of the ladder operators, right? So in practice that means that we have to deal with commuting of long sequences of the ladder operators such that they destroy the vacuum bra and in the process pick up terms that have delta functions with momentum variables. This becomes non trivial even for a string of 8, 10 ladder operators. It could be done by hand but at the expense of time. The obvious way to deal with this is to write code! Is anybody aware of such code in either Fortran, C or any other language? I must not be the first one to think of it, it must have been done before. At least, where would be a good place to start looking for this? What are good site that have Fortran libraries devoted to QFT or physics in general? Thanks in advance.