Topic: Entmod & IF, why does it work?

[Hangman]

Afternoon everyone,

I have been struggling with a simple task and am wondering why the IF statement doesn't need a PROGN when used in the ENTMOD function.
Here's an example:

Code: [Select]

              (entmod
                [color=green](if (assoc 8 (setq eList (entget ent)))[/color] ; testexpr
                  [color=purple](subst (cons 8 "Text") (assoc 8 eList) eList)[/color] ; thenexpr
                  [color=blue](append eList '((8 . "Text")))[/color] ; elseexpr
                )
              ) ; _entmod

According to the help file,

IF
Conditionally evaluates expressions
(if testexpr thenexpr [elseexpr])

So how does this end up running both scenarios, ...  or does it?

[Jeff_M]

It doesn't run them both. It is saying:

(entmod elist)

(elist) is being defined as either the original that HAS an (assoc 8) in the list modified to suit OR the original list with the new (assoc 8) dotted pair added to it)

(if (elist contains a value for (assoc 8))
   then change it
   else add it
)