Controlled Viewport Pan Lisp Problem

[Lee Mac]

I'm not a big fan ( eq )

 

Just look at the example of the help files:

 

(setq f1 '(a b c))

(setq f2 '(a b c))

 

(setq f3 f2)

 

Compare f1 and f3:

 

Command: (eq f1 f3)

 

nil

 

For that matter:

 

(eq f1 f2) returns nil

 

It's just not that intuitive for me.

 

I do use it for comparing ENAMEs in that are they are bound to symbols.

 

(=) converts strings to their ASCII numbers and compares them that way.

 

(= "Z" "z") returns nil

 

-David

 

Thanks David,

 

I think I've seen something like that before

 

http://www.theswamp.org/index.php?topic=29839.msg354144#msg354144

[David Bethel]

Another one can be strange is (/=)

 

(/= 1 1 2 1 1) returns nil ( at least up until 2000 )

 

whereas (not (= 1 1 2 1 1)) returns T

 

I never quite understood the reasoning:

 

AutoLISP Reference

 

Note that the behavior of /= does not quite conform to other LISP dialects. The standard behavior is to return T if no two arguments in the list have the same value. In AutoLISP, /= returns T if no successive arguments have the same value; see the examples that follow.

 

Examples

 

(/= 10 20) returns T

(/= "you" "you") returns nil

(/= 5.43 5.44) returns T

(/= 10 20 10 20 20) returns nil

 

(/= 10 20 10 20) returns T

 

Note in the last example that although there are two arguments in the list with the same value, they do not follow one another, and thus /= evaluates to T.

[SteveK]

Note in the last example that although there are two arguments in the list with the same value, they do not follow one another, and thus /= evaluates to T.

Interesting...

If (= 1 1 2 2) & (/= 1 1 2 2) both return nil does that mean /= compares them in pairs whereas = compares all args?

 

Then (not (= 1 1 2 1 1)) returns T makes sense because (= 1 1 2 1 1) is nil.

 

Are these results consistant with Lisp in general or just AutoLisp?

[David Bethel]

SteveK

 

Interesting...

does that mean /= compares them in pairs

 

as sequential pairs as I understand it:

 

(/= 10 20 10 20) returns T

 

would compare (= 10 20) then (= 20 10) then (= 10 20)

 

None of these return T so the /= call returns T

 

Are these results consistant with Lisp in general or just AutoLisp?

It's just AutoLsip as far as I know. -David