Topic: BricsCAD: Problem with ((if booleVarP and not) T)?

[roy_043]

In BricsCAD I have a problem with this (see line 3 of the code):

Code - Auto/Visual Lisp: [Select]

1. (setq booleVarP T)
2. ((if booleVarP + -) 2 5) => 7 (OK).
3. ((if booleVarP and not) T) => Error! See below.
4.  
5. (setq booleVarP nil)
6. ((if booleVarP + -) 2 5) => -3 (OK).
7. ((if booleVarP and not) T) => nil (OK).

Why is there this error?: no function definition <(IF BOOLEVARP AND NOT)> ; expected FUNCTION at [EVAL]

[ronjonp]

Not sure why it's throwing the error but in AutoCAD it generates this:
; error: cannot apply special form: AND

[roy_043]

@ ronjonp:
Well at least it seems that BricsCAD is compatible. But like you I do not understand why there is an error.

[hmspe]

Could it be that 'and' and 'not' are lisp functions?  Selecting an operator this way makes some sense, but I would not expect to be able to select a function this way.  I'm more surprised that line 7 appears to work than that line 3 does not.  That said, I'm not sure that line 7 is really evaluating what we think it is.

[roy_043]

Code: [Select]

(setq booleVarP T)
((if booleVarP and not) T)   => Error!
((if booleVarP and not) nil) => Error!

(setq booleVarP nil)
((if booleVarP and not) T)   => nil
((if booleVarP and not) nil) => TIf there is no error the evaluation seems correct.
BTW: Using (or) instead of (and) does not solve this.

[Lee Mac]

Given the error returned in AutoCAD, I presume that the problem is caused by the and function being a Special Form, and hence evaluating arguments in a different manner to not.

This is confirmed when using other Special Forms, such as foreach:

Code - Auto/Visual Lisp: [Select]

1. _$ (setq x t)
2. T
3. _$ ((if x foreach) y '(1 2 3) (princ y))
4. T
5. ; error: cannot apply special form: FOREACH

Or or:

Code - Auto/Visual Lisp: [Select]

1. _$ (setq x t)
2. T
3. _$ ((if x or not) t)
4. ; error: cannot apply special form: OR

[MP]

You just have to play nice with the interpreter:

(apply (if t 'and 'not) '(T)) => T

(apply (if nil 'and 'not) '(T)) => nil

[roy_043]

Thanks guys.