float64

Property	Value
Size	8 bytes (64 bits)
Format	IEEE 754 binary64 (double precision)
Approximate range	±2.2 × 10-308 to ±1.8 × 10308
Decimal precision	~15–16 digits
Literal suffix	f64
Hardware support	Native on all supported targets

float64 is the default floating-point type in Rux — float is a built-in alias for it. It is fully IEEE 754-2019 compliant. Special values (Inf, -Inf, NaN) are supported, and division by zero produces Inf or NaN rather than a fatal error.

Literals

A floating-point literal written without an annotation or suffix is inferred as float64:

let e = 2.718281828459045;       // float64 (inferred)
let a: float64 = 1.0;            // explicit annotation
let b = 1.0f64;                  // type suffix

Decimal and scientific forms are both accepted:

let avogadro = 6.022e23;   // 6.022 × 10²³
let planck   = 6.626e-34;  // 6.626 × 10⁻³⁴

See Literals for the full grammar.

Typical Use Cases

• Scientific computing
• Financial calculations
• General-purpose numeric code

Arithmetic

Operator	Description	Compound
+	Addition	+=
-	Subtraction	-=
*	Multiplication	*=
/	Division	/=
%	Remainder	%=
**	Exponentiation	n/a

let a: float64 = 10.0;
let b: float64 = 3.0;

let sum  = a + b;   // 13.0
let quot = a / b;   // 3.3333333333333335
let rem  = a % b;   // 1.0

Both operands must share the same type; mixed-width expressions require an explicit cast. Arithmetic rounds to nearest (ties to even), unary negation (-x) flips the sign, and results that exceed the range overflow to Inf. Subtracting nearly equal values loses significant digits (catastrophic cancellation) — reorder the computation or use a wider type when accuracy matters.

Division by zero never fails: it yields signed infinity, and 0.0 / 0.0 yields NaN. Inf and NaN then propagate — Inf - Inf and Inf * 0.0 are both NaN.

let p =  1.0 / 0.0;  //  Inf
let n = -1.0 / 0.0;  // -Inf
let u =  0.0 / 0.0;  //  NaN

Comparison

Operator	Description	Result
==	Equal	bool
!=	Not equal	bool
<	Less than	bool
<=	Less than or equal	bool
>	Greater than	bool
>=	Greater than or equal	bool

Both operands must have the same type; comparing a different float width, or a float with an integer, is a compile-time error — cast explicitly first.

NaN is unordered: every comparison involving it returns false, including NaN == NaN. Detect it with IsNan, never ==. For the same reason, avoid == between computed results and compare within a tolerance instead:

let x = 0.1 + 0.2;
let close = Abs(x - 0.3) < 1.0e-9;  // not  x == 0.3

Conversion

Rux implicitly widens to any larger float type, so no precision is lost. Narrowing must be explicit and rounds to nearest (ties to even).

let x: float64 = 1.5;
let wide: float128 = x;      // widening — implicit
let narrow = x as float32;   // narrowing — explicit cast

Float-to-integer conversions are always explicit and truncate toward zero; the reverse (int→float) widens implicitly. Casting NaN or Inf to an integer raises a fatal error in debug builds.

let whole = x as int32;      // 1     truncates toward zero
let back: float64 = 100;     // 100.0 int→float, implicit

See Also

• float — the alias used for float64 in everyday code
• float32 — narrower, hardware-native alternative