Re: Calling a function with undefined symbol

[Heime]

------- Original Message -------
On Monday, October 31st, 2022 at 9:24 AM, Jean Abou Samra <jean@abou-samra.fr> 
wrote:


> > Le 31 oct. 2022 à 09:59, Heime heimeborgia@protonmail.com a écrit :
> > 
> > Yes, I have got really confused about what symbols are exactly. Even
> > after reading several times. I have never seen anybody make a symbol,
> > only variables. So, what is a symbol?
> 
> 
> 
> 
> Imagine parents who are planning to have a child and decide they will call 
> it, say Deborah. They will say things like “I like the name Deborah better 
> than Mary”. Those are sentences about the names themselves, not some 
> children. The names don’t need children in order to exist as words. Then, the 
> child is born and sentences like “Deborah weighs 3kg” (referring to the child 
> named Deborah) start to make sense.
> 
> When you do 'symbol in Lisp, this gives you a bare name, or a “symbol”. With 
> symbol-value, you get what value is associated with this symbol, if any (the 
> child with that name). But you don’t need a value bound to the symbol (a 
> child called Deborah) before you start using the symbol itself (the name 
> “Deborah”).

The Lisp manual says that a symbol is an object with a name.  Then a variable 
(setq thevar 4) has an associated symbol 'thevar.
And the function "(defun thefun ()" also has an associated symbol "'thefun".  
Furthermore one can make just a symbol, let us say 'go,
which can be passed as an argument to a function "(defun mbcomplt (arg)" using 
(mbcomplt 'go).  Then inside the function on can test
whether the symbol exists with (eq arg 'go).  Even though we only have a name 
without a values.  Is this a good basic understanding 
of a symbol?