Hi Alex,
Thanks for the reply, that was how I understood the intention of that text
as well. It is ambiguous though, considering the discussion of
auto-gensyms later in the page mentions:
"If a symbol is non-namespace-qualified and ends with '#', it is resolved
to a generated symbol with the same name to which '_' and a unique id have
been appended. e.g. x# will resolve to x_123. All references to that symbol
within a syntax-quoted expression resolve to the same generated symbol."
Which is to say, the text describes symbol names and using '#'.
Anyways, I get that '#' usage remains open for interpretation and later
design decisions. I thought maybe because it was already used in
auto-gensyms and because of how read() and syntaxQuote() relate in
LispReader, it might mean that '#' became a definitive part of permitted
symbol name characters. I think a second look at that made me realize it
could still be reinterpreted.
So, although I like the use of '#' for my use case, it's easy enough to
revise my design to use a different character here.
That said, wouldn't it better then for the compiler be made more
restrictive now (i.e., only permit symbol names with '#' within syntax
quote)? For example, the following compiles and runs fine in the REPL:
(let [a# 4 b#a 3] (println a# b#3))
Because you're telling me I can not depend on '#' for symbols, I will have
to make this change in some released code, where I had been using '#' in
keywords, and that's a breaking change for my API. It would have been much
nicer for me if such reserved things are treated as errors, so that I don't
write valid code now that is at risk of breaking later.
There are also other characters, such as '$', '%', '=', '&', '|', '>', '<',
that also work now but are not listed in the website text regarding symbol
names. Some, like '=', '>', and '<' are in common use as part of symbol
names. ('$' seems often used with as->). As a user, I see one description
in text, but in real world code I see other things in use, and that makes
it confusing. It would be useful (to me at least) to have this be a little
clearer what is reserved and what is not.
Thanks!
steven
On Monday, November 7, 2016 at 8:38:28 PM UTC-5, Alex Miller wrote:
>
>
>
> On Monday, November 7, 2016 at 6:33:49 PM UTC-6, Steven Yi wrote:
>>
>> Hi All,
>>
>> I wanted to understand whether '#' may be treated as a valid character
>> for symbols. The Clojure site [1] has:
>>
>> "Symbols begin with a non-numeric character and can contain
>> alphanumeric characters and *, +, !, -, _, ', and ? (other characters
>> may be allowed eventually)."
>>
>
> The general advice here is that the characters listed here are guaranteed
> to be valid now and in the future. Characters not listed here may be
> accepted now or used within Clojure, but are not guaranteed to work in the
> future.
>
>
>> I realized I was using # today in a symbol without thinking much of
>> it. However, the syntax highlighting in Vim marked it oddly when it
>> was at the end of the symbol name versus in the middle of the name.
>> (The use case is denoting musical notes using lists of symbols, such
>> as '(c c# d eb) ).
>>
>
> Same as above - this works now, but is not guaranteed to always be valid.
>
> auto-gensyms also employ # as part of symbol names, but I do not know
>> if that should be considered a kind of special case.
>>
>
> Same as above - Clojure may use these symbols to mean special things (like
> auto gensyms in syntax quote), but that right is reserved for Clojure.
>
>
>> Any clarifications appreciated!
>> steven
>>
>> [1] - http://clojure.org/reference/reader
>>
>
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to [email protected]
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
"Clojure" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
