In

The in constraint restricts a node’s value to a predefined set of allowed values. It is most commonly used to limit text or numeric nodes to a controlled vocabulary or a fixed set of constants.

When applied to text nodes, the behavior of this constraint can be influenced by the case sensitivity flag.

Type Matrix

The following table summarizes which node types support the in constraint and how membership is evaluated.

Node Type	S	Value Type	Details
Integer		ValueList	Valid only if the integer value appears in the list of integers.
Boolean
Float		ValueList	Valid only if the floating-point value appears in the list. Equality must be evaluated using a platform-consistent strategy (for example, with a tolerance that accounts for IEEE rounding).
Text		ValueList	Valid only if the text matches one of the listed text values.
Date
Time
DateTime
Bytes		ValueList	Valid only if the byte sequence matches one of the listed byte sequences.
TimeDelta
RegEx
Value
ValueList
ValueMatrix
Section
SectionList
SectionWithTexts
NotValidated

Rules

1. List Membership: The value of the node must exactly match one of the values listed in in.

2. Type Alignment: Each value listed in in must have the same type as the constrained node.

   Mixing types (for example, constraining a text node with integers) is invalid and must be rejected by the validator.

3. No Duplicate Entries: Each value in the in list must be unique.

   Duplicate entries provide no additional meaning and must be treated as an error in the validation rules document.

4. Floats and Equality: For floating-point values, equality must be determined using a platform-consistent strategy that accounts for precision and rounding behavior.

   This ensures that values such as 0.1 behave consistently across different validators and platforms.

5. Case Sensitivity: Text comparisons using in are case-insensitive by default.

   This behavior can be changed using the case_sensitive flag. See The Case Sensitive Flag for details.

Example

The following example restricts mode to one of three predefined text values:

[server.mode]
type: "text"
in: "idle", "scanning", "connecting"

[server]
mode: "scanning"

[server]
mode: "shutdown"  # ERROR: Must be one of "idle", "scanning", "connecting"