[swift-evolution] [Proposal]: Free the '$' Symbol!

[Chris Lattner]

We need a token to be unambiguously an operator or identifier - we can have different rules for the leading and subsequent characters though.

-Chris

> On Jan 3, 2016, at 6:02 PM, Jacob Bandes-Storch <jtbandes at gmail.com> wrote:
> 
> Is it considered infeasible for any characters to be allowed in both identifiers and operators?
> 
>> On Sun, Jan 3, 2016 at 1:23 PM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> > On Jan 2, 2016, at 11:53 PM, Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org> wrote:
>> >
>> >> Swift currently does not allow operators to use $ - I assume because the grammar reserves it in one place: `implicit-parameter-name`.  I don't see why an entire class of identifiers has been eliminated, so I propose $ instead be reclassified as an `operator-character` so it can be used mixed in with other such characters, but prevents the introduction of `$Identifier`-style declarations that might conflict with implicit parameters.
>> >
>> > I believe the reason you don't see any other $ variables is that they're reserved for the debugger and REPL.
>> >
>> >       brent at Brents-MacBook-Pro ~/D/Code> swift
>> >       Welcome to Apple Swift version 2.1.1 (swiftlang-700.1.101.15 clang-700.1.81). Type :help for assistance.
>> >         1> "foo"
>> >       $R0: String = "foo"
>> >         2> print($R0)
>> >       foo
>> 
>> Right.  That said, our current operator space (particularly the unicode segments covered) is not super well considered.  It would be great for someone to take a more systematic pass over them to rationalize things.
>> 
>> -Chris
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