Naming Rules

C3 introduces fairly rigid naming rules to reduce ambiguity and make the language easy to parse for tools.

As a basic rule, all identifiers are limited to a-z, A-Z, 0-9 and _. The initial character can not be a number. Furthermore, all identifiers are limited to 31 character.

Structs, unions, enums and faults

All user defined types must start with A-Z after any optional initial _ and include at least 1 lower case letter. Bar, _T_i12 and TTi are all valid names. _1, bAR and BAR are not. For C-compatibility it’s possible to alias the type to a external name using the attribute “extern”.

struct Foo @cname("foo")
{
    int x;
    Bar bar;
}

union Bar
{
    int i;
    double d;
}

enum Baz
{
    VALUE_1,
    VALUE_2
}

faultdef OOPS, LOTS_OF_OOPS;

Variables and parameters

All variables and parameters except for global constant variables must start with a-z after any optional initial _. ___a fooBar and _test_ are all valid variable / parameter names. _, _Bar, X are not.

int theGlobal = 1;

fn void foo(int x)
{
    Foo foo = getFoo(x);
    theGlobal++;
}

Global constants

Global constants must start with A-Z after any optional initial _. _FOO2, BAR_FOO, X are all valid global constants, _, _bar, x are not.

const int A_VALUE = 12;

Enum / Fault definitions

enum and faultdef definitions follow the same naming standard as global constants.

enum Baz
{
    VALUE_1,
    VALUE_2
}

faultdef OOPS, LOTS_OF_OOPS;

Struct / union members

Struct and union members follow the same naming rules as variables.

Modules

Module names may contain a-z, 0-9 and _, no upper case characters are allowed.

module foo;

Functions and macros

Functions and macros must start with a-z after any optional initial _.

fn int anotherFunction()
{
}

macro justDoIt(x)
{
    justDo(x);
}

C3 recommended code style

While C3 doesn’t mandate a particular style of naming, the standard library nonetheless uses naming conventions which are recommended for official bindings and standard library contributions:

alias MyInt = int;    // Types use PascalCase
struct SomeStructType
{
    int a_field;      // Members use snake_case
    double foo_baz;
}
int some_global = 1;  // Globals use snake_case
fn void some_function(int a_param) // Functions and parameters use snake_case
{
    int foo_bar = 4;  // Locals use snake_case
}
// Methods use snake_case, and the first parameter is usually called "self"
fn void SomeStructType.call_me(self, int a)
{
    some_function(self.a_field + a);
}
// Macros use snake_case
macro @some_macro(a)
{
    return a + a;
}
const MY_FOO = 123; // Constants use SCREAMING_SNAKE_CASE

So in short:

1. Types use PascalCase
2. Constants use SCREAMING_SNAKE_CASE
3. Everything else uses snake_case

Brace style is often a controversial topic. The C3 standard library uses Allman brace style:

fn int allman(int foo)
{
    if (foo > 2)
    {
        foo++;
    }
    else
    {
        foo *= foo;
    }
    return foo;
}

For canonical C3 code outside of the stdlib and vendor (the official binding repository), prefer either Allman or K&R:

fn int k_and_r(int foo)
{
    if (foo > 2) {
        foo++;
    } else {
        foo *= foo;
    }
    return foo;
}

Regarding tab-vs-spaces, contributions to the C3 stdlib or vendor should use tabs for indentation and spaces for formatting.