Re: Is there a way of setting a variable only when it exists?

[Emanuel Berg]

tomas wrote:

> "Customizable variables", also called "user options", are
> global Lisp variables whose values can be set through the
> Customize interface. Unlike other global variables, which
> are defined with `defvar' [...] customizable variables are
> defined using the `defcustom' macro. In addition to calling
> `defvar' as a subroutine, `defcustom' states how the
> variable should be displayed in the Customize interface, the
> values it is allowed to take, etc.

So an interface is used so that an interface can be displayed
... and those interfaces are ... the same?

You hear how it sounds.

Hands of data! There can be many ways to set data. But after
the data is set nothing should be left _how_ and no special
treatment should later be allowed based on what interface was
used ...

interface |~| data |#| programming logic (code)
           ↑        ↑
           ↑        ↑
           ↑   reinforced
           ↑    concrete
           ↑      wall
         brick
         wall

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