On Sat, Mar 24, 2012 at 1:44 AM, Cedric Greevey <cgree...@gmail.com> wrote:
> On Sat, Mar 24, 2012 at 1:28 AM, Sean Corfield <seancorfi...@gmail.com> wrote:
>> On Fri, Mar 23, 2012 at 8:44 PM, Cedric Greevey <cgree...@gmail.com> wrote:
>>> #{foo bar baz} is somewhat ugly. It occurs to me that one could modify
>>> the reader to additionally accept
>>>
>>> {{foo bar baz}}
>>
>> My concern is that {{1 2 3 4}5} is currently legal - a map with a map
>> as a key and 5 as the value. That means that the reader couldn't tell
>> if {{ introduced your set notation or the start of a nested map
>> without looking arbitrarily far ahead. And that problem gets worse if
>> you encounter {{{ or {{{{ or... {{{ could introduce a nested map, a
>> map of your sets or one of your sets containing a map...
>
> The other objections are fair enough -- matters of taste. But the
> above is a technical problem with a simple fix: make one pass over the
> source, converting it into a rudimentary AST whose nodes just look
I think the word "reader" above applies both to the human and computer
kinds. You've only addressed the problem for the computer. A user
would still have to look at the end of the collection to know if it is
a set or map (or use editor).
> As for the aesthetics, what I like about {{...}} is that the
> delimiters are symmetrical, unlike #{...}, and it would allow one to
> reserve use of the # mark to, mostly, closures, so # would stand out
> more as typically indicating a lambda.
Sorry to break it to you, but # is used in many places other than
lambdas, so even if you remove it from #{} you still have foo#, #^foo,
#^{foo bar}, #'foo, #"foo", #_foo, #foo{1 2}, #foo[1 2], and others
I've probably forgotten.
One option you have is to use Emacs to replace #{} and #() with
something distinctive looking.
(dolist (mode '(clojure-mode slime-repl-mode))
(eval-after-load mode `(font-lock-add-keywords
',mode
(mapcar
(lambda (pair)
`(,(car pair)
(0 (progn (compose-region (match-beginning 1)
(match-end 1)
,(cadr pair))
nil))))
`(("\\(#\\){" "∈")
("\\(#\\)(""ƒ")
("(\\(fn\\)[\[[:space:]]" "λ")
("(\\(comp\\)[\[[:space:]]" "∘")
("(\\(range\\)[\[[:space:]]" "ℝ")
("(\\(apply \+\\)[\[[:space:]]" "∑")
("(\\(Math/pi\\)[\[[:space:]]" "π")
("(\\(->\\)[\[[:space:]]" "→")
("(\\(partial\\)[\[[:space:]]" "þ")
("(\\(complement\\)[\[[:space:]]" "¬")
;; not working
;; ("Math/pi[:space:]" "π")
;; ("(\\(apply \+\\)[\[[:space:]]" "∑")
)))))
Cheers,
Scott
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