Dagger comes with 3 functions for user input, one for each type of data value. To input an integer, use "readint", to input a decimal, use "readdec", and to input a string, use "readstr".
dagger> set {a} 0 # Initialize variable
()
dagger> readint a
(0)
Okay, something happend.... Variables in dagger are immutable, they can't be changed, so what we're going to do is read the variable while initializing it a second time, as so:
dagger> set {a} 0
()
dagger> = {a} (readint a)
3 # I inputted 3
dagger> a
3