Operators

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Operators

The Alloy configuration syntax uses a standard set of operators. All operations follow the PEMDAS order of mathematical operations.

Arithmetic operators

OperatorDescription
+Adds two numbers.
-Subtracts two numbers.
*Multiplies two numbers.
/Divides two numbers.
%Computes the remainder after dividing two numbers.
^Raises a number to the specified power.

String operators

OperatorDescription
+Concatenate two strings.

Comparison operators

OperatorDescription
==Returns true when two values are equal.
!=Returns true when two values aren’t equal.
<Returns true when the left value is less than the right value.
<=Returns true when the left value is less than or equal to the right value.
>Returns true when the left value is greater than the right value.
>=Returns true when the left value is greater than or equal to the right value.

You can use the equality operators == and != with any operands.

The operands in ordering operators <, <=, >, and >= must be orderable and of the same type. The results of these comparisons are:

  • Boolean values are equal if both are either true or false.
  • Numerical (integer and floating-point) values are ordered in the usual way.
  • String values are ordered lexically, byte-wise.
  • Objects are equal if all their fields are equal.
  • Arrays are equal if their corresponding elements are equal.

Logical operators

OperatorDescription
&&Returns true when both the left and right values are true.
||Returns true when either the left or right value is true.
!Negates a boolean value.

Logical operators work with boolean values and return a boolean result.

Assignment operator

The Alloy configuration syntax uses = as the assignment operator.

An assignment statement can only assign a single value. Each value must be assignable to the attribute or object key.

  • You can assign null to any attribute.
  • You can assign numerical, string, boolean, array, function, capsule, and object types to attributes of the corresponding type.
  • You can assign numbers to string attributes with an implicit conversion.
  • You can assign strings to numerical attributes if they represent a number.
  • You can’t assign blocks.

Brackets

BracketsDescription
{ }Define blocks and objects.
( )Group and prioritize expressions.
[ ]Define arrays.

For example, the following code uses curly braces and square brackets to define an object and an array.

alloy 
obj = { app = "alloy", namespace = "dev" }
arr = [1, true, 7 * (1+1), 3]

Access operators

OperatorDescription
[ ]Access a member of an array or object.
.Access a named member of an object or an exported field of a component.

You can use the Alloy access operators to retrieve nested values. Use square brackets to access zero-indexed array elements or object fields by enclosing the field name in double quotes. Use the dot operator to access object fields without double quotes or component exports.

alloy 
obj["app"]
arr[1]

obj.app
local.file.token.content

If you use the [ ] operator to access a non-existent object member, the result is null.

If you use the . operator to access a non-existent named member of an object, an error occurs.