Then study & gt It studies the construction of mathematical systems, such as building a closed computing system.

It is not easy to learn complex variable function and real variable function before learning. You need to know some basic contents of km set theory. The basis of functional is the property of point set.

& lt& lt topology >; > Further, we need the foundation of modern algebra and functional.

If you want to teach yourself, it is suggested that you need to lay a good foundation in mathematical analysis, advanced algebra, complex/real variables and so on before you can start functional.