Re: uninterned symbols as Tree-IL constants

[BT Templeton]

address@hidden (Ludovic Courtès) writes:

> Hi,
>
> BT Templeton <address@hidden> skribis:
>
>> I noticed that when uninterned symbols are used as Tree-IL constants,
>
> I thought literal (constant) symbols in Elisp were interned.  You seem
> to imply this isn’t always the case; can you explain?

Since Elisp lacks hygienic macros, macros typically use uninterned
symbols for variable names used in their expansions in order to avoid
name clashes.

There are also a couple other ways to use uninterned symbols as
literals: you can use `eval', and Elisp supports Common Lisp's `#:foo'
syntax. Sharpsign-colon is rare in Elisp, but potentially useful for
testing special forms without polluting the global namespace:

  (progn
    '#1=#:foo
    (setq #1# 42)
    #1#) ; => 42

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