Skip to content

Basic types and values

C3 provides a similar set of fundamental data types as C: integers, floats, arrays and pointer. On top of this it expands on this set by adding slices and vectors, as well as the any and typeid types for advanced use.


C3 has signed and unsigned integer types. The built-in signed integer types are ichar, short, int, long, int128, iptr and isz. ichar to int128 have all well-defined power-of-two bit sizes, whereas iptr has the same number of bits as a void* and isz has the same number of bits as the maximum difference between two pointer. For each signed integer type there is a corresponding unsigned integer type: char, ushort, uint, ulong, uint128, uptr and usz.

intyes-2^312^31 - 132
longyes-2^632^63 - 164
int128yes-2^1272^127 - 1128
uintno02^32 - 132
ulongno02^64 - 164
uint128no02^128 - 1128

On 64-bit machines iptr/uptr and isz/usz are usually 64-bits, like long/ulong. On 32-bit machines on the other hand they are generally int/uint.

Integer constants

Numeric constants typically use decimal, e.g. 234, but may also use hexadecimal (base 16) numbers by prefixing the number with 0x or 0X, e.g. int a = 0x42edaa02;. There is also octal (base 8) using the 0o or 0O prefix, and 0b for binary (base 2) numbers:

Numbers may also insert underscore _ between digits to improve readability, e.g. 1_000_000.

a = -2_000;
b = 0o770;
c = 0x7f7f7f;

For decimal numbers, the value is assumed to be a signed int, unless the number doesn’t fit in an int, in which case it is assumed to be the smallest signed type it does fit in (long or int128).

For hexadecimal, octal and binary, the type is assumed to be unsigned.

A integer literal can implicitly convert to a floating point literal, or an integer of a different type provided the number fits in the type.

Constant suffixes

If you want to ensure that a constant is of a certain type, you can either add an explicit cast like: (ushort)345, or use an integer suffix: 345u16.

The following integer suffixes are available:


Note how uint also has the u suffix.


A bool will be either true or false. Although a bool is only a single bit of data, it should be noted that it is stored in a byte.

bool b = true;
bool f = false;

Character literals

A character literal is a value enclosed in '``'. Its value is intepreted as being its ASCII value for a single character.

It is also possible to use 2, 4 or 8 character wide character literals. Such are interpreted as ushort, uint and ulong respectively and are laid out in memory from left to right. This means that the actual value depends on the endianess of the target.

  • 2 character literals, e.g. 'C3', would convert to an ushort.
  • 4 character literals, e.g. 'TEST', converts to an uint.
  • 8 character literals, e.g. 'FOOBAR11' converts to an ulong.

The 4 character literals correspond to the layout of FourCC codes. It will also correctly arrange unicode characters in memory. E.g. Char32 smiley = '\u1F603'

Floating point types

As is common, C3 has two floating point types: float and double. float is the 32 bit floating point type and double is 64 bits.

Floating point constants

Floating point constants will at least use 64 bit precision. Just like for integer constants, it is possible to use _ to improve readability, but it may not occur immediately before or after a dot or an exponential.

C3 supports floating points values either written in decimal or hexadecimal formats. For decimal, the exponential symbol is e (or E, both are acceptable), for hexadecimal p (or P) is used: -2.22e-21 -0x21.93p-10

While floating point numbers default to double it is possible to type a floating point by adding a suffix:

f32 or ffloat


Arrays have the format Type[size], so for example: int[4]. An array is a type consisting of the same element repeated a number of times. Our int[4] is essentially four int values packed together.

For initialization it’s sometimes convenient to use the wildcard Type[*] declaration, which infers the length from the number of elements:

int[3] abc = { 1, 2, 3 }; // Explicit int[3]
int[*] bcd = { 1, 2, 3 }; // Implicit int[3]

Read more about initializing arrays in the chapter on arrays.


Slices have the format Type[]. Unlike the array, a slice does not hold the values themselves but instead presents a view of some underlying array or vector.

Slices have two properties: .ptr, which retrieves the array it points to, and .len which is the length of the slice - that is, the number of elements it is possible to index into.

Usually we can get a slice by taking the address of an array:

int[3] abc = { 1, 2, 3 };
int[] slice = &abc; // A slice pointing to abc with length 3

Because indexing into slices is range checked in safe mode, slices are vastly more safe providing pointer + length separately.


Similar to arrays, vectors use the format Type[<size>], with the restriction that vectors may only form out of integers, floats and booleans. Similar to arrays, wildcard can be used to infer the size of a vector:

int[<*>] a = { 1, 2 };

Vectors are based on hardware SIMD vectors, and supports many different operations that work on all elements in parallel, including arithmetics:

int[<2>] b = { 3, 8 };
int[<2>] c = { 7, 2 };
int[<2>] d = b * c; // d is { 21, 16 }

Vector initialization and literals work the same way as arrays, using { ... }

String literals

Like C, string literals is text enclosed in " ... " just like in C. These support escape sequences like \n for line break and need to use \" for any " inside of the string.

C3 also offers raw strings which are enclosed in ` `. Inside of a raw string, no escapes are available, and to write a `, simply double the character:

char* foo = `C:\foo\bar.dll`;
char* bar = `"Say ``hello``"`;
// Same as
char* foo = "C:\\foo\\bar.dll";
char* bar = "\"Say `hello`\"";

String literals are special in that they can convert to several different types: String, char and ichar arrays and slices and finally ichar* and char*.

Base64 and hex data literals

Base64 literals are strings prefixed with b64 to containing Base64 encoded data, which is converted into a char array at compile time:

// The array below contains the characters "Hello World!"
char[*] hello_world_base64 = b64"SGVsbG8gV29ybGQh";

The corresponding hex data literals convert a hexadecimal string rather than Base64:

// The array below contains the characters "Hello World!"
char[*] hello_world_hex = x"4865 6c6c 6f20 776f 726c 6421";

Pointer types

Pointers have the syntax Type*. A pointer is a memory address where one or possibly more elements of the underlying address is stored. Pointers can be stacked: Foo* is a pointer to a Foo while Foo** is a pointer to a pointer to Foo.

The pointer type has a special literal called null, which is an invalid, empty pointer.


The void* type is a special pointer which implicitly converts to any other pointer. It is not “a pointer to void”, but rather a wildcard pointer which matches any other pointer.

Printing values

Printing values can be done using io::print, io::printn, io::printf and io::printfn. This requires importing the module std::io.

import std::io; // Get the io functions.
fn void main()
int a = 1234;
double d = 13.03e-04;
char[*] hex = x"4865 6c6c 6f20 776f 726c 6421";

If you run this program you will get:

[72, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100, 33]

To get more control we can format the output using printf and printfn:

import std::io;
fn void main()
int a = 1234;
double d = 13.03e-04;
char[*] hex = x"4865 6c6c 6f20 776f 726c 6421";
io::printfn("a was: %d", a);
io::printfn("b in hex was: %x", b);
io::printfn("d in scientific notation was: %e", d);
io::printfn("Bytes as string: %s", (String)&hex);

We can apply the standard printf formatting rules, but unlike in C/C++ there is no need to indicate the type when using %d - it will print unsigned and signed up to int128, in fact there is no support for %u, %lld etc in io::printf. Furthermore, %s works not just on strings but on any type:

import std::io;
enum Foo
fn void main()
int a = 1234;
uint128 b = 0xFFEEDDCC_BBAA9988_77665544_33221100;
Foo foo = BCD;
io::printfn("a: %s, b: %d, foo: %s", a, b, foo);

This prints:

a: 1234, b: 340193404210632335760508365704335069440, foo: BCD