The two numbers are multiplied together, and the * (product or multiplication) function returns a value of 1.75. In this example, the innermost expression (* 2 0.875) is evaluated first. The following is an example of a nested mathematical expression in AutoLISP: (+ 0.01 (* 2 0.875)) The evaluation process of AutoLISP expressions is similar to the order of operations in mathematics. When expressions are nested, they are always evaluated from the innermost expression to the outermost. AutoLISP expressions can be nested inside of each other. The following are some examples of AutoLISP expressions:Īs an AutoLISP program grows in complexity, so will the expressions that you create. The ! (exclamation point) character can only be used at the AutoCAD Command prompt and is used to return the current value of an AutoLISP variable. In addition to an AutoLISP expression starting with a ( (open parenthesis), an expression can also start with the ! character. Most function topics also include example code to help you get started with that function.Īt first glance, the syntax used by AutoLISP expressions in a program can be intimidating but with a little bit of practice and time you will get used to it.
The AutoCAD Help system contains a list of the available functions that can be used in an AutoLISP program. The following shows the syntax that is used for an AutoLISP expression: (function_name ) Usually, the first element in the list is the name of a function, and the following elements are called arguments, which provide the values that the function will process.
A list is a structure enclosed by parentheses. Creating custom routines with the AutoLISP programming language is an excellent way for you to automate and extend AutoCAD to the way that you want to work.ĪutoLISP is based on the LISP (LISt Processing) programming language.
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