Hi Ess,
On 01/08/2017 02:33 AM, Ess Kay wrote:
Why wouldn't Peter's syntax proposal suffice
For any syntax to work (in ANY context) you need to be able to distinguish
between the use of that syntax and the specification of an identifier (e.g.
a module, package, class, field or method name) which happens to match that
syntax. Let's take Peter's string #"\\u0022\\\"" as an example. How is
that string to be interpreted? Is it an example of the proposed syntax that
should be interpreted as the 11 character identifier \\u0022\\\" or is it a
14 character identifier starting with # and ending with to double quotes?
If this sequence of characters appear in source at position where
identifier is expected:
#"\\u0022\\\""
then they are interpreted as an identifier with following characters:
\u0022\"
This is unambiguous because otherwise the syntax of "plain" identifier
(as opposed to "exotic" identifier) doesn't allow it to start with
character #.
If parser encounters character # followed by double quote, it knows it
is a start of exotic identifier.
Module, package, class, field and method names can legally start with the 2
characters #" and end in a double quote. That is why Peter's syntax would
not work.
Why? If the name of identifier starts with #"... then such identifier
can only be expressed in the syntax of exotic identifiers, therefore you
have to write it in the source as:
#"#\"..."
This is the difficulty when you specify that almost any
character and character combination is a valid in an identifier.
I see no difficulty here.
Regards, Peter
I thought your problem was that users needed a way to express
"crazy identifiers" in _your_ (or other Java-like) script languages.
My discussion of the problem of crazy identifiers in JAR manifests was
more of "parting shot". It is very easy to be ultra flexible in a
specification. It is very concise and even aesthetically pleasing.
However, it can be much, much harder to actually support that ultra
flexibility in the practice. Problems can occur in unexpected places. Such
is life.
