modules

Modules are reusable Envision code blocks imported by scripts or other modules. Modules are not executable: they do not produce dashboards and cannot contain read, write, or show statements.

Only exported elements are visible outside the module. Non-exported values remain local to the module.

Export and import

The export keyword marks elements that can be imported elsewhere. The import keyword loads those elements.

// Module "/sample/my-module"
export const myHello = "Hello"
export const myWorld = "World!"

import "/sample/my-module" as M with
  myHello
  myWorld

show scalar "" with "\{myHello} \{myWorld}"

When a module is imported without a with block, its elements are accessed through the module alias as a namespace.

import "/sample/my-module" as M

show scalar "" with "\{M.myHello} \{M.myWorld}"

Exported vector functions

Modules can export pure, process, and vector functions. An exported vector function is declared with export def vector. Its table parameters and vector arguments are supplied by the importing script, so the module does not need to read the caller’s data itself.

Call the function through the module alias, or import its name with a with block. Both forms retain the function<<Tables>>(arguments) syntax. See exporting a vector function for the paired module and caller example.

Inline documentation

Triple-slash comments (///) immediately preceding an exported element are attached as inline documentation.

// Module "/sample/my-docs"

/// Greeting prefix.
export const myHello = "Hello"

Chained imports

A module can import another module. Circular dependencies are rejected.

// Module "/sample/my-base"
export const myNumber = 10

// Module "/sample/my-next"
import "/sample/my-base" as M
export const myNumber = 13 + M.myNumber

Type annotations on import

Import entries may re-specify types for clarity.

// Module "/sample/my-types"
export const myText = "Hello World!"
export const myNumber = 42

import "/sample/my-types" as M with
  myText : text
  myNumber : number

show summary "" with myText, myNumber

Export limitations

Only scalar values, tuples of scalar values, user-defined functions, enums, table comprehensions, and schemas can be exported.

Exported module values and exported table comprehensions must resolve to compile-time constants. Consequently, runtime-built values such as ranvar, zedfunc, and embedding cannot be exported as module values or inside exported tables. Exported functions and exported schemas may still return or declare those types.

See also

• export
• import