DEF function-name ( variable-name [ , variable-name ... ] ) = expression

   Synopsis:
      Defines a one-line function

   Notes:
      An Axbasic function has a name and an argument list consisting of one or
         more parameters.
      Before evaluating the function, Axbasic assigns the value of each argument
         to the parameter variable (in the example below, the value 10 is
         assigned to x). The expression is evaluated and becomes the return 
         value of the function.
      Once defined in a DEF statement, the function can be used in an 
         expression.
      'variable-name' must be a scalar variable (not an array variable).
      For multi-line functions, use subroutines (see the help for SUB and 
         GOSUB).

   Examples:
      ! Define a function to multiply by 10
      DEF Multiply (x) = x * 10

      ! This statement prints the value 50
      PRINT Multiply (5)
      ! This statement prints the value 1000
      PRINT 10 * Multiply (10)

      ! Every defined function must have at least one argument, even if the
      ! function doesn't need one
      DEF Roll (x) = int(rnd(6) + 1)
      ! Roll the die to print a value between 1 and 6
      PRINT Roll
