Hi. I've been learning quantum mechanics from different sources and I'm starting to notice that they have really different ways of treating certain things. For example: in some places Griffiths works with wavefunctions, while Sakurai works using eigenkets. This confuses me. As I understand, wavefunctions are simply the coefficients of a state's expansion on the position basis. How can then a operator "act" on a wavefunction? Thank you for your time.