How to control the output of a lisp function ?

[jbreard]

Hello everyone,

 

I'm a total newbie with lisp and so have a total newbie's problem.

 

I've translated an algorithm into lisp to compute the Fresnel integrals C(x) and S(x) of a given number x. The code works quite well and in the end I do have the value of C and S(x) stored in two local variables c and s. But after that, I want to use those numbers into another function. How can I tell autolisp to give me a list of c and s for example ? I tried to define another variable cs like this:

(setq cs (list c s)) but then how will the programm know that I want cs for an output and not c, s or any other variable I have on the code ?

 

I hope I've been clear enough.

 

Thank you

 

Jacques

[MSasu]

In AutoLISP the result of evaluation of last line of code is what a function will return. So,

 

- to return the said list:

(defun MyFunc()
... ;your code
(setq cs (list c s))
)

 

- to don't return:

(defun MyFunc()
... ;your code
(setq cs (list c s))
(princ)
)

[jbreard]

Dear Mircea,

 

thanks so much. I get it now. My last line was the (princ) indeed that I had copied from other lisp example without totally understanding it.

 

I'm working on these functions to plot clothoid curves in the end. If anyone is interested out there...

 

Regards,

 

Jacques

[MSasu]

You're welcome.

Please keep in mind that the PRINC/PRIN1 as last line can be legit in many cases; is usually placed as last line in function that don't need to return or in user defined command to exit quietly - that it, without a value or nil printed on command prompter.

[Lee Mac]

Note also that the extra 'cs' variable is not necessary:

 

(defun YourFunction ( / c s )
   (setq c 1.41421
         s 1.61803
   )
   (list c s)
)

Calling the function at the Visual LISP IDE Console:

 

_$ (YourFunction)
(1.41421 1.61803)

 

Also, always remember to declare your local variables ('c' & 's' in the above example).

[jbreard]

Mmmm,

 

Thanks Lee Mac. I can see that now. Much more elegant indeed !

Well, i'm moving on on my small project and write this first lisp to draw clothoid curves.

I shall present it to you all very soon if I can make it work fine

 

Regards,

 

Jacques