"and", no not the function. Help with evaluating 2 expressions

[Anonymous]

Hi all.

Need to call on your expertise again. 

I find many times where I want to say "and" in my routines, For example in "plain" English:

"If Angle1 is less than 0 and  Angle2 is greater than 0, then SETQ....blah blah blah

Is there a function or expression that lets you do this?

Ultimately find a work around with multiple if statements or cond. It always seems to get messy and convoluted.

Is there a simpler way to evaluate/compare to arguments like that?

Any help is appreciated.

Thank you

[Shneuph]

You're saying you're looking for an alternative to the AND function?

(If (and

      (< Angle1 0)

      (> Angle2 0)

      );and

  (setq .....)

  );if

[ВeekeeCZ · Accepted solution]

And actually IS the function.

Your example.

(if (and (< angle1 0)
	 (> angle2 0)
	 )
  (setq blah "blah"))

It could even be used in following syntax. The result is the same.

(and (< angle1 0)
     (> angle2 0)
     (setq blah "blah")
     )

[Anonymous]

Thank You! Your examples were quite helpful

I was confused by the cryptic definition of AND I was looking at.

"...Arguments
expr Any expression.
Return Values
Nil, if any of the expressions evaluate to nil; otherwise T. If and is issued
without arguments, it returns T.
Examples
Command: (setq a 103 b nil c "string")
"string"
Command: (and 1.4 a c)
T
Command: (and 1.4 a b c)
nil"

your examples make perfect sense.

Thanks Again.

[ВeekeeCZ]

---

@Anonymous wrote:

Thank You! Your examples were quite helpful

I was confused by the cryptic definition of AND I was looking at.

"...Arguments
expr Any expression.
Return Values
Nil, if any of the expressions evaluate to nil; otherwise T. If and is issued
without arguments, it returns T.
Examples
Command: (setq a 103 b nil c "string")
"string"
Command: (and 1.4 a c)
T
Command: (and 1.4 a b c)
nil"

your examples make perfect sense.

Thanks Again.

---

The number 1.4 inside of and does not make much sence. It's always T. But testing variables (and a b c) for not nil, that makes the sence.

BTW an empty string variable (setq a "") is True.

[steve_carson]

Thanks for the info regarding an empty string, BeekeeCZ.

I think it's weird that an empty string is T, but an empty list is nil...

Command: (and "")
T

Command: (and '())
nil

Command: (= '() nil)
T

Steve

[Kent1Cooper]

---

@steve_carson wrote:

.... 

I think it's weird that an empty string is T, but an empty list is nil...

....

---

Just to add another to that list of empty things that may or may not be nil:

The result of (ssget), if nothing is selected or found, is nil, not an empty selection set.  But empty selection sets can "exist" -- if you remove everything from a selection set with (ssdel) functions, or start an empty one via (ssadd) with no items-do-add argument, it may be empty and have an (sslength) of 0, but it still "exists" and is not nil.

[john.uhden]

Kudos to you!
Do you remember Stephan Koster too?
He's the one that got me hooked on anding.
Technically, it stops further evaluations if any returns nil.

[ВeekeeCZ]

---

@john.uhden wrote:
Kudos to you!
Do you remember Stephan Koster too?
He's the one that got me hooked on anding.
Technically, it stops further evaluations if any returns nil.

---

Thanks! Unfortunately I have no idea how this guy is, although I know you've noticed him before. But I remember were I saw this 'odd' usage of and function for the first time - it made me a little thinking about it. It was @Kent1Cooper 's ReportAngle routine HERE.

Another interesting constructions using similar principle are...

(or dst
    (initget 5)
    (setq dst (getdist "\nSet distance: "))
    )

;;;;;

(setq dst (cond ((getdist "\nSet distance <10>: "))
		(10)))

[martti.halminen]

The rules about truth values in the Lisp language family (except Scheme) can be expressed quite simply:

1. The symbol NIL and the empty list are the same object, there is no way to distinguish between them.

2. NIL is the only thing that is considered false in a boolean context (IF, COND, AND, OR etc.)

3. Anything else whatsoever is considered as true.

-- 

[martti.halminen]

I'd write the last one slightly differently:

(setq dst (cond ((getdist "\nSet distance <10>: "))
		(T 10)))

but that is just a style preference.

This is a little contrived construction, usually only seen in AutoLISP.

That would be legal also in other Lisps, but there this can be done in a simpler way, because in other Lisps OR returns the value of the last thing it evaluated, instead of T:

(setq dst (or (getdist "\nSet distance <10>: ")
              10))