You can start by using AutoLISP functions on AutoCAD command prompt. Before we start, let's understand the structure / syntax of AutoLISP function. How AutoLISP function is written?
Any AutoLISP function will start with opening parenthesis '(' and it will end with closing parenthesis ')', in between it will contain the function and its arguments.
For examples suppose we want to make sum of two nos using AutoLISP function. Then it will be written as
(+ 10 35.6)
Please note that, function started with opening parenthesis '(', after that name of the function, in this case '+', arguments 10 & 35.6 and closing bracket ')'.
Above syntax needs to be followed for any AutoLISP function. You can try following on AutoCAD command prompt:
(+ 15 23.65 256.89)
(- 25 3)
(/ 250 25)
As we know AutoLISP functions starts with opening parenthesis '(' & ends with closing parenthesis ')'. If you forgot to write the closing parenthesis then AutoCAD shows following symbol:
This symbol indicate that your AutoLISP function is not complete and you have missed something. You can complete your syntax by writing remaining part of AutoLISP function you have forgot.
Watch video tutorials on AutoLISP Getting Started