Lesson no. 2
 
An AutoLisp function is always between parenthesis.So, when you open a parenthesis, you must tell what function to use, followwith the arguments when needed.

(function argument1 argument2 ...)

It is very important to put the right amountof arguments to a function. Some functions  have one argument, somecan have
two or more, some other can have optionalarguments.
    Take, for example, the+ function. We must provide at least two arguments:

(+ numbre1 numbre2 [numbre3 numbre4....])

Here, arguments in brackets [] are optionals,but the arguments "numbre1" and "numbre2" are required.

(+ 23 34) ® 57
(+ 23 34 154 -22) ®189

    Be careful of the spaceswhen you write a program. Sometimes you can put some spaces, some othertimes they are forbidden. So, to simplify, just follow theses two simplesrules:

1- NEVER put a space after an open parenthesis
2- ALWAYS put a space elsewhere
 

• With the mathematical functions, the result canbe an integer or a real. If the formula includes only integer, the resultwill be an integer. But, you need only one real in the formula to havea real for result. Be careful, this can be tricky.

 

 

(+ 23 34) ® 57®integer
(+ 23 34.0) ® 57.0®real
(/ 3 4) ® 0 ®integer(see the false result)
(/ 3 4.0) ® 0.75®real(ahhh!! thats better)

You can try this in the command prompt area

COMMAND: (+ 23 34)
57
COMMAND:

This is a list of the mathematical functions:
 
 

FUNCTION	SYNTAXE	EXAMPLE	RESULT
ADD	(+N1 N2 ...)	(+ 2 4)	2 + 4 = 6
SUBTRACT	(- N1 N2 ...)	(- 10 2 3)	(10 - 2) - 3 = 5
MULTIPLY	(* N1 N2 ...)	(* 3.0 8)	3.0 * 8 = 24.0
DIVIDE	(/ N1 N2 ...)	(/ 48 8 3)	(48 ¸ 8) ¸3 = 2
REMAIN	(REM N1 N2 ...)	(REM 10 3)	(10 ¸ 3) = 3 RESTE 1
SQUARE ROOT	(SQRTN1)	(SQRT 9)	Ö 9 = 3
ABSOLUTE VALUE	(ABSN1)	(ABS -2.5)	| -2.5 | = 2.5
EXPONENTIAL	(EXPN1)	(EXP 2)	e² = 7.38906
X TO THE  Y POWER	(EXPTN1 N2)	(EXPT 4 3)	4³ = 64
NATURAL LOG	(LOGN1)	(LOG 7.38906)	Ln 7.38906 = 2.71828
GREATER COMMON DENOMINATOR	(GCDN1 N2)	(GCD 25 30)	5
SINUS	(SIN N1)	(SIN 1.5708)	SINUS ( ¶ ¸ 2) = 1.0
COSINUS	(COSN1)	(COS 0)	COSINUS 0 = 1.0
ARC TANGENT	(ATANN1 [N2])	(ATAN 1.0)	0.785398

For the 3 last functions, the arguments mustbe in radians. A constant exist....PI = 3.14159....Ex: (* 2 pi) ®6.28319
 

• Dont forget that we can nest functions....


( 8 + 4 ) / ( 5 - 2) = 4   in Lisp would be ® (/ (+ 8 4 ) (- 5 2 ))

We solve the more nested parenthesis first
(+ 8 4) ® 12
(- 5 2) ® 3
(/  12 3) ® 4