6.3 | Names

Identifiers are used to give names to several classes of language objects and refer to these objects by name later:

- value names (syntactic class `value-name`),
- value constructors (constant -- class `cconstr-name` -- or non-constant -- class `ncconstr-name`),
- labels (`label-name`),
- variant tags (`tag-name`),
- type constructors (`typeconstr-name`),
- record fields (`field-name`),
- class names (`class-name`),
- method names (`method-name`),
- instance variable names (`inst-var-name`),
- module names (`module-name`),
- module type names (`modtype-name`).

These nine name spaces are distinguished both by the context and by the capitalization of the identifier: whether the first letter of the identifier is in lowercase (written `lowercase-ident` below) or in uppercase (written `capitalized-ident`). Underscore is considered a lowercase letter for this purpose.

Naming objects

`value-name` | ::= | `lowercase-ident`
| | | `(` `operator-name` `)`
`operator-name` | ::= | `prefix-symbol` | `infix-symbol` | `*` | `=` | `or` | `&` | `:=`
`cconstr-name` | ::= | `capitalized-ident`
| | | `false`
| | | `true`
| | | `[` `]`
| | | `(` `)`
`ncconstr-name` | ::= | `capitalized-ident`
| | | `::`
`label-name` | ::= | `lowercase-ident`
`tag-name` | ::= | `capitalized-ident`
`typeconstr-name` | ::= | `lowercase-ident`
`field-name` | ::= | `lowercase-ident`
`module-name` | ::= | `capitalized-ident`
`modtype-name` | ::= | `ident`
`class-name` | ::= | `lowercase-ident`
`inst-var-name` | ::= | `lowercase-ident`
`method-name` | ::= | `lowercase-ident`

As shown above, prefix and infix symbols as well as some keywords can be used as value names, provided they are written between parentheses. Keywords such as '::' and 'false' are also constructor names. The capitalization rules are summarized in the table below.

Name space | Case of first letter
Values | lowercase
Constructors | uppercase
Labels | lowercase
Variant tag | uppercase
Type constructors | lowercase
Record fields | lowercase
Classes | lowercase
Methods | lowercase
Modules | uppercase
Module types | any

Note on variant tags: the current implementation accepts lowercase variant tags in addition to uppercase variant tags, but we suggest you avoid lowercase variant tags for portability and compatibility with future OCaml versions.

Referring to named objects

`value-path` | ::= | `value-name`
| | | `module-path` `.` `lowercase-ident`
`cconstr` | ::= | `cconstr-name`
| | | `module-path` `.` `capitalized-ident`
`ncconstr` | ::= | `ncconstr-name`
| | | `module-path` `.` `capitalized-ident`
`typeconstr` | ::= | `typeconstr-name`
| | | `extended-module-path` `.` `lowercase-ident`
`field` | ::= | `field-name`
| | | `module-path` `.` `lowercase-ident`
`module-path` | ::= | `module-name`
| | | `module-path` `.` `capitalized-ident`
`extended-module-path` | ::= | `module-name`
| | | `extended-module-path` `.` `capitalized-ident`
| | | `extended-module-path` `(` `extended-module-path` `)`
`modtype-path` | ::= | `modtype-name`
| | | `extended-module-path` `.` `ident`
`class-path` | ::= | `class-name`
| | | `module-path` `.` `lowercase-ident`

A named object can be referred to either by its name (following the usual static scoping rules for names) or by an access path `prefix` `.` `name`, where `prefix` designates a module and `name` is the name of an object defined in that module. The first component of the path, `prefix`, is either a simple module name or an access path `name`1 `.` `name`2 ..., in case the defining module is itself nested inside other modules. For referring to type constructors or module types, the `prefix` can also contain simple functor applications (as in the syntactic class `extended-module-path` above), in case the defining module is the result of a functor application.
Label names, tag names, method names and instance variable names need not be qualified: the former three are global labels, while the latter are local to a class.