Primitive Types

IonPath provides a rich set of built-in types covering integers, floats, strings, dates, and special types. Each type has a fixed wire encoding and mappings to C# and TypeScript.

Integer Types

Signed and unsigned integers from 8-bit to 128-bit.

Ion Type	C#	TypeScript	Size	Description
i1	sbyte	number	8 bits	Signed byte (-128 to 127)
i2	short	number	16 bits	Signed short
i4	int	number	32 bits	Signed integer
i8	long	bigint	64 bits	Signed long
i16	Int128	bigint	128 bits	Signed 128-bit integer
u1	byte	number	8 bits	Unsigned byte (0 to 255)
u2	ushort	number	16 bits	Unsigned short
u4	uint	number	32 bits	Unsigned integer
u8	ulong	bigint	64 bits	Unsigned long
u16	UInt128	bigint	128 bits	Unsigned 128-bit integer

ℹ

The naming convention follows byte count: i4 = 4 bytes = 32 bits. u prefix means unsigned, i means signed.

Floating-Point Types

Ion Type	C#	TypeScript	Size	Description
f2	Half	number	16 bits	IEEE 754 half precision
f4	float	number	32 bits	IEEE 754 single precision
f8	double	number	64 bits	IEEE 754 double precision

Special Types

Ion Type	C#	TypeScript	Description
void	void	void	No value — used for methods with no return
bool	bool	boolean	Boolean true/false
string	string	string	UTF-8 text
guid	Guid	string	128-bit UUID
bigint	BigInteger	bigint	Arbitrary-precision integer
bytes	byte[] / IonBytes	Uint8Array	Raw binary data
uri	Uri	string	URI/URL

Date & Time Types

Ion Type	C#	TypeScript	Description
datetime	DateTime	Date	UTC date and time
dateonly	DateOnly	string	Date without time component
timeonly	TimeOnly	string	Time without date component
duration	TimeSpan	number	Time span / duration

Generic Wrappers

These built-in generic types wrap other types:

Wrapper Description

Maybe<T> Optional value. Shorthand: T?. Null on the wire when absent.

Array<T> Variable-length sequence. Shorthand: T[]. CBOR array encoding.

Partial<T> Sparse update — only modified fields are serialized. Shorthand: ~T.

Usage Example

msg UserProfile {
    id: u4;                  // unsigned 32-bit integer
    name: string;             // UTF-8 text
    email: string?;            // optional string (Maybe<string>)
    avatar: bytes?;            // optional binary data
    score: f8;                // double-precision float
    createdAt: datetime;       // UTC timestamp
    tags: string[];            // array of strings
    largeId: u8;              // 64-bit unsigned (bigint in TS)
    uniqueRef: guid;          // 128-bit UUID
}