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Comments

FUME supports comments throughout authoring. The same comment syntax works in expression-oriented mappings, parenthesized orchestration blocks, and FLASH blocks.

The two comment forms are:

  • // single-line comments
  • /* block comments */

Single-line comments​

Use // when the note only needs to run to the end of the current line.

// Prepare a stable identifier once
$patientId := $uuid("examplecare-patient-001");

Instance: $patientId
InstanceOf: Patient
* active = true // Source system marks this as active

Block comments​

Use /* ... */ for inline notes or multi-line explanation blocks.

/* This mapping accepts either one patient object
   or an array of source rows that normalize to patients. */
(
  $displayName := firstName & " " & lastName;
  $displayName
)

Where comments can appear​

You can place comments:

  • on their own line between steps
  • after an expression or FLASH rule
  • inside parenthesized orchestration blocks
  • inside indented FLASH rule sets
(
  // Build shared values once for the rest of the mapping
  $patientId := $uuid("examplecare-patient-001");
  $displayName := firstName & " " & lastName;

  (
    Instance: $patientId
    InstanceOf: Patient
    * name.text = $displayName /* Reuse the computed display value */
  )
)

Whitespace and readable structure​

Blank lines are allowed and are useful for separating logical steps in a mapping.

Whitespace also helps make orchestration blocks easier to scan, especially when a mapping mixes variable bindings, helper calls, and one or more FLASH blocks. In FLASH specifically, indentation still carries structure, so aligned rule nesting matters even when blank lines and comments are present.

FLASH declaration order​

FLASH declarations keep their own ordering rules. When a declaration includes Instance:, InstanceOf: must appear as the next non-comment line.

Instance: $uuid("examplecare-patient-001")
// This comment is allowed here
InstanceOf: Patient

That rule belongs to FLASH parsing. The comment syntax itself stays consistent throughout FUME authoring.