ABSTRACT
T of another variation of function composition. Itsconstraints are very interesting, namely the first one: the core program cannot do IO. For our term-frequency task, that reads files and outputs a result on the screen, this constraint poses a puzzling problem: how can we do it if the functions can’t read files such as the Pride and Prejudice text and can’t print things on the screen? Indeed, how can one write programs these days that don’t interact one way or another with the user, the file system, and the network while the program is executing?
