ABSTRACT
This chapter deals with functions with explicit arguments, explicit result, and at most a simple loop. It discusses editing of user-defined functions and relevant system commands and introduces random number generation. Each primitive A Programming Language (APL) function conforms to the mathematical notion of a function; each has one or two arguments and generates a uniquely determined value, which is called the result of the function. A user-defined function may use the results of other user-defined functions that produce explicit results simply by referring to them by name within the body of the function. When a user-defined function halts in mid-computation due to an error, APL returns to immediate execution mode in a modified state; namely, the function execution is suspended. Sometimes several functions have their execution suspended at the same time. Basically APL is ready for modifications of functions and variables and a resumption of the computation.
