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Package Declaration

In the Cangjie programming language, package declarations begin with the keyword package, followed by the package names from the root package to the current package, separated by .. Package names must be valid ordinary identifiers (excluding raw identifiers). For example:

> Note:
>
> In the current Windows platform version, package names do not support Unicode characters. Package names must be valid ordinary identifiers containing only ASCII characters.

The package declaration must appear as the first non-empty, non-comment line in a source file, and all source files within the same package must maintain consistent package declarations.

In Cangjie, package names should reflect the relative path of the current source file from the project's source root directory src, with path separators replaced by dots. For example, if the package's source code is located under src/directory_0/directory_1 and the root package name is pkg, the package declaration in the source code should be package pkg.directory_0.directory_1.

Important considerations:

- The folder name containing the package must match the package name.
- The default name for the source root directory is src.
- Packages in the source root directory may omit package declarations, in which case the compiler will assign them the default package name default.

Given the following source directory structure:

The package declarations in a.cj, b.cj, c.cj, and main.cj can be:

Additionally, package declarations must not cause naming conflicts: sub-packages cannot share names with top-level declarations in the current package.

Here are some error examples:

cangjie

package pkg1      // root package pkg1
package pkg1.sub1 // sub-package sub1 under root package pkg1

cangjie

// file 1
// Comments are accepted
package test
// declarations...

// file 2
let a = 1 // Error, package declaration must appear first in a file
package test
// declarations...

text

// The directory structure is as follows:
src
`-- directory_0
    |-- directory_1
    |    |-- a.cj
    |    `-- b.cj
    `-- c.cj
`-- main.cj

cangjie

// a.cj
// in file a.cj, the declared package name must correspond to relative path directory_0/directory_1.

package default.directory_0.directory_1

cangjie

// b.cj
// in file b.cj, the declared package name must correspond to relative path directory_0/directory_1.

package default.directory_0.directory_1

cangjie

// c.cj
// in file c.cj, the declared package name must correspond to relative path directory_0.

package default.directory_0

cangjie

// main.cj
// file main.cj is in the module root directory and may omit package declaration.

main(): Int64 {
    return 0
}

cangjie

// a.cj
package a
public class B { // Error, 'B' is conflicted with sub-package 'a.B'
    public static func f() {}
}

cangjie

// b.cj
package a.B
public func f {}

cangjie

// main.cj
import a.B // ambiguous use of 'a.B'

main() {
    a.B.f()
}