Lexical Rules
Slice's lexical rules are very similar to those of C++, C#, and Java.
Comments
Slice definitions permit both the C and the C++ style of writing comments:
/*
* C-style comment.
*/
// C++-style comment extending to the end of this line.Keywords
Slice uses a number of keywords, which must be spelled in lowercase. For example, class and dictionary are keywords and must be spelled as shown. There are two exceptions to this lowercase rule: Object and Value are keywords and must be capitalized as shown.
Identifiers
Identifiers begin with an alphabetic character followed by any number of alphabetic characters or digits. Underscores are also permitted in identifiers with the following limitations:
an identifier cannot begin or end with an underscore
an identifier cannot contain multiple consecutive underscores
Given these rules, the identifier get_account_name is legal but not _account, account_, or get__account.
Slice identifiers are restricted to the ASCII range of alphabetic characters and cannot contain non-English letters, such as Å.
Case Sensitivity
Identifiers are case-insensitive but must be capitalized consistently. For example, TimeOfDay and TIMEOFDAY are considered the same identifier within a naming scope. However, Slice enforces consistent capitalization. After you have introduced an identifier, you must capitalize it consistently throughout; otherwise, the compiler will reject it as illegal. This rule exists to permit mappings of Slice to languages that ignore case in identifiers as well as to languages that treat differently capitalized identifiers as distinct.
Escaped Identifiers
It is possible to use a Slice keyword as an identifier by prefixing the keyword with a backslash, for example:
struct dictionary // Error!
{
// ...
}
struct \dictionary // OK
{
// ...
}
struct \foo // Legal, same as "struct foo"
{
// ...
}The backslash escapes the usual meaning of a keyword; in the preceding example, \dictionary is treated as the identifier dictionary. The escape mechanism exists to permit keywords to be added to the Slice language over time with minimal disruption to existing specifications: if a pre-existing specification happens to use a newly-introduced keyword, that specification can be fixed by simply prepending a backslash to the new keyword. Note that, as a matter of style, you should avoid using Slice keywords as identifiers (even though the backslash escapes allow you to do this).
It is legal (though redundant) to precede an identifier that is not a keyword with a backslash — the backslash is ignored in that case.
Language Mapping
A Slice identifier maps to an identical JavaScript identifier. For example, the Slice identifier Clock becomes the JavaScript identifier Clock.
A single Slice identifier often results in several JavaScript identifiers. For example, for a Slice interface named Greeter, the generated JavaScript code uses the identifiers Greeter and GreeterPrx.
You can change this mapping and specify your own JavaScript identifier with the js:identifier metadata directive. For example, we can remap Greeter to Receptionist as follows:
["js:identifier:Receptionist"]
interface Greeter { ... } The resulting JavaScript symbols are Receptionist and ReceptionistPrx.
When you use a JavaScript reserved word such as export as a Slice identifier, use js:identifier to remap this identifier in the generated JavaScript code. Without this remapping, the generated JavaScript code is invalid.