Expressions

An expression is anything that produces a value: a literal, a variable, a calculation, or a function call. You use expressions to compute what a script stores, compares, and returns.

let my_var = 100 + 20.5
let is_active = true || false
let text = concat("my text", some_other_text_var)

Expressions can include variables, literal values, placeholders, operators, and parentheses that control evaluation order.

let total = (price * quantity) + tax

Commands such as get and set are statements, not expressions, so you cannot nest them inside an expression: to_int(get k) is a syntax error. Read the value into a variable first with let v = get k, then use to_int(v).

Operators

Arithmetic Operators

Basic arithmetic:

• + Addition
• - Subtraction
• * Multiplication
• / Division

Example:

let result = (10 + 5) * 2

The value of result is 30.

Dividing two integers gives an integer, truncated toward zero: 7 / 2 is 3 and -7 / 2 is -3. Make one operand a float to keep the fraction: 7 / 2.0 is 3.5.

Division by zero, int64 overflow, and a float result that would be NaN or infinity are script errors. See Numbers for exact bounds and failure behavior. Numeric equality is exact; use nearly_equals when a floating-point calculation should compare with a tolerance.

Logical Operators

Combine boolean conditions:

• &&: Returns true if both expressions are true
• ||: Returns true if at least one expression is true
• ! or not: Inverts the boolean value of an expression

Example:

let is_valid = (age > 18) && (has_id == true)
let should_retry = (error != null) || (timeout_occurred)
let is_guest = !is_registered

Logical operators require boolean operands and short-circuit when the left side determines the result. This makes guard expressions safe:

let safe = divisor != 0 && total / divisor > 10

Comparison Operators

Compare two values:

• == Equal to (= also works inside an expression)
• != Not equal to (<> also works)
• < Less than
• <= Less than or equal to
• > Greater than
• >= Greater than or equal to

Example:

let is_adult = age >= 18
let has_access = role == "admin"
let is_different = score1 != score2

Comparison operators return true or false.

Operator Precedence

Operators higher in this table bind tighter. Operators on the same row are evaluated left to right; unary - and not apply to the operand on their right.

Precedence	Operators
1 (highest)	[ ] array index
2	!, not
3	unary -
4	*, /
5	+, -
6	<, >, <=, >=
7	==, =, !=, <>
8	&&
9	||
10 (lowest)	.. range

So 2 + 3 * 4 is 14, a || b && c is a || (b && c), and 0..n + 1 is 0..(n + 1).

not binds tighter than a comparison, unlike in Python or SQL: not x == 5 parses as (not x) == 5. When x is a number, that is a script error, because not requires a boolean. Write not (x == 5) or x != 5 instead.

Range Operators

Create an array of integers from a minimum to a maximum:

let my_range = 1..10

This creates an array:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Use ranges for iteration, indexing, or generating value sets. Ranges include both bounds. A range with a start greater than its end is empty, and a single evaluated range is capped at 100000 elements.

For detailed edge-case behavior, see Script Semantics.

Function Calls

Kahuna Script has built-in functions for strings (including to_json), math, time, type checks and casts, and values and collections (count, rev, expires). Deployments can add their own user-defined functions.

A function call uses the following syntax:

function_name(arg1, arg2, ...)

Examples:

let name = upper("alice")
let a_number = round(10.55, 1)
let json_str = to_json([10, 42, 30])

upper returns "ALICE", round returns 10.6, and to_json serializes the array to JSON.

Statement-Result Guards

not found, not set, not deleted, and not extended return booleans based on the last completed read, write, delete, or extend respectively. They preserve that result across unrelated statements and require an earlier operation of the relevant kind. See Statement-Result Guards for exact scope, successful delete/extend handling, and batched statement order.