Topic: (AutoLISP the language) ARITHMETIC the AutoLISP way

[Mark]

My intentions of this thread, and others, is to show the basics of using the AutoLISP programming language in AutoCAD.

I am basically following the book AutoLISP Programming Principles and Techniques by Rod Rawls and Mark Hagen.
https://www.amazon.com/Autolisp-Programming-Principles-Rod-Rawls/dp/1566371961?ie=UTF8&*Version*=1&*entries*=0

Please ask lots of questions.

If you are an experienced programmer please help by adding additional exercises.

Thanks!

[Mark]

Basic math: 1 + 2 = 3
AutoLISP function: (+ 1 2) Make note of the spaces in the function.

1 + 2 + 3 = 6
(+ 1 2 3) = 6

3 - 1 = 2
(- 3 1) = 2
(- 20 10 5) = 5
(- 50 -5) = 55

1 * 2 = 3
(* 1 2) = 3
(* 10.525 25.125) = 264.441
(* 50.2 20 2.133) = 2141.53

16 ÷ 2 = 16
(/ 16 = 2
(/ 16 8.0) = 2.0

[snownut2]

except for 1+ or 1-   

Sorry couldn't help it, in LISP there's always a catch.

[Mark]

except for 1+ or 1-   

Sorry couldn't help it, in LISP there's always a catch.

Show us an example please.

[snownut2]

ok

Code - Auto/Visual Lisp: [Select]

1.  
2. (1+ 2) = 3
3. (1- 2) = 1
4.  
5.  

I usually use these in a while loop if i am counting either up or down, example.

Code - Auto/Visual Lisp: [Select]

1. (setq cnt 0)
2. (while (< cnt 20)
3.   ..............
4.   (setq cnt (1+ cnt))
5. )
6.  

[Mark]

More advanced math. From the book

18 - [(3 + 6 + 9) ÷ (9 - 6)] - 12

Work from the deepest levels out.
(+ 3 6 9) (- 9 6)
(/ (+ 3 6 9) (- 9 6))
(- 18 (/ (+ 3 6 9) (- 9 6)))
(- (- 18 (/ (+ 3 6 9) (- 9 6))) 12)

[Mark]

Using arithmetic on the command line.

Code: [Select]

Command: OFFSET
Current settings: Erase source=No  Layer=Source  OFFSETGAPTYPE=0
Specify offset distance or [Through/Erase/Layer] <Through>: (* 0.235 15)
3.525


[ribarm]

The topic that may be of interest, at least when arithmetic is an issue...

https://www.theswamp.org/index.php?topic=51268.0

[roy_043]

... Maybe using CODE tags is a good idea...

Small addition: Negation:

Code: [Select]

(- 1) => -1
(- -1) => 1


[rkmcswain]

Using arithmetic on the command line.

Code: [Select]

Command: OFFSET
Current settings: Erase source=No  Layer=Source  OFFSETGAPTYPE=0
Specify offset distance or [Through/Erase/Layer] <Through>: (* 0.235 15)
3.525


Note that you must include one real number if you want a real number result.
Example:

Code: [Select]


Command: OFFSET
Current settings: Erase source=No  Layer=Source  OFFSETGAPTYPE=0
Specify offset distance or [Through/Erase/Layer] <Through>: (/ 15 4)
3

***compared to ***

Command: OFFSET
Current settings: Erase source=No  Layer=Source  OFFSETGAPTYPE=0
Specify offset distance or [Through/Erase/Layer] <Through>: (/ 15 4.0)
3.75



[Peter2]

..
1 * 2 = 3
(* 1 2) = 3
...

??

[kdub_nz]

Mark was just making sure you were awake Peter .. well done.