Why must references use the :: qualifier?

← Syntax and Structure Rules · Ref: Q726

EK9 uses the 'references' block to import symbols from other modules for short-name access. Each reference must use the fully qualified form: module.path::SymbolName. Using a bare name without the module qualifier triggers E01010.

REFERENCES SYNTAX

The references block appears after the module declaration:

  defines module my.app
    references
      net.customer.geometry::Circle
      net.customer.geometry::Pi

The '::' separator divides the module path (left) from the symbol name (right).

FULLY QUALIFIED INLINE

You can also use fully qualified names inline without a references block:

  circle <- net.customer.geometry::Circle(5.0)

This works anywhere but is verbose for repeated use.

AFTER IMPORTING

Once referenced, use the short name directly:

  references
    net.customer.geometry::Circle
  defines program
    Demo()
      c <- Circle(5.0)

ALPHABETICAL ORDER

References must be listed in alphabetical order (E11026).

MULTI-FILE WORKSPACE

This Q&A demonstrates cross-module references: the referenced module (qa.syntaxrules.refsupport) is defined in a separate companion file, just as it would be in a real EK9 project.

See Q6 for module organization. See Q142 for cross-module constants.

Example

defines module qa.syntaxrules.modulereference

  references
    qa.syntaxrules.refsupport::Formatter
    qa.syntaxrules.refsupport::MaxItems

  defines program

    ModuleReferenceDemo()
      stdout <- Stdout()

      //Short name access via references block
      formatted <- Formatter("hello")
      stdout.println(formatted)
      stdout.println(`Max items: ${MaxItems}`)

      //Fully qualified inline access also works
      formatted2 <- qa.syntaxrules.refsupport::Formatter("world")
      stdout.println(formatted2)

Companion: QA0726_referenced_module.ek9

#!ek9
defines module qa.syntaxrules.refsupport

  defines constant
    MaxItems <- 50

  defines function

    Formatter() as pure
      -> text as String
      <- rtn as String: `[${text}]`

//EOF

Coming from another language?

Java: import com.example.MyClass with dot-separated path. Python: from module import Class. Go: import path/package. Rust: use crate::module::Type. C#: using Namespace.Type. EK9: references block with module.path::SymbolName using :: separator.

Keywords: cross, access, symbol, module, E01010, syntax, reference, qualifier, import