Type Casts

The as operator converts a value from one type to another — an explicit cast. Rux performs no implicit conversions between distinct types, so wherever a value's type does not already match what is required, an as cast makes the conversion visible in the source.

let n: int64 = bigValue as int64;

The left operand is the value to convert; the right operand is the target type. The result is the value expressed in the target type.

Numeric Conversions

Arithmetic and comparison operands must share a type. Convert one side explicitly when the types differ:

let left: int32 = 10;
let right: int64 = 20;

let invalid = left < right;           // error: different operand types
let valid = (left as int64) < right;  // OK

Signed and unsigned integers also require an explicit cast. Choose a target type wide enough to represent the value correctly:

let count: uint32 = 100;
let delta: int32 = count as int32;

Boolean Conversions

Boolean types are distinct from numeric types, so conversion in either direction is explicit. Conversion between boolean widths also uses as:

let wide: bool32 = flag as bool32;

Casting an integer to bool is legal but easy to misuse. When deriving a boolean from a number, prefer an explicit comparison — it states the intent directly:

let active = n != 0;     // preferred — clear and explicit
let opaque = n as bool;  // legal, but the intent is less obvious

See Boolean Types for the full conversion rules.

Casting After a Type Test

as is the companion of the is type test. Test the type first, then cast inside the branch where the test has already succeeded:

if shape is Circle {
    let circle = shape as Circle;  // safe — the test just succeeded
    Print(circle.radius);
}

as vs. is

as and is are companion type operators:

Operator	Question it answers	Result
as	Give me this value as type T	the value as T
is	Does this value have type T?	bool

Precedence

as shares precedence level 2 with is — just below the unary operators and above arithmetic, so it binds tighter than the surrounding operators. This means left as int64 < right reads as (left as int64) < right:

let valid = left as int64 < right;

Parentheses are still worth adding when they make the intent clearer. See Operator Precedence for the complete table.

See Also

• Type Tests — the companion is operator
• Arithmetic Operations — where mismatched numeric types need a cast
• Primitive Data Types — the types you convert between