Builtins

A builtin is a type or function provided by the compiler without an import. Examples include int, string, List, Option, and panic.

This page lists every builtin and links to a page that explains it in full.

Two layers

Beans builds its builtins in two ways. You do not need to think about this while you write code, but it helps to know it once.

• Some builtins are implemented by the C runtime and reached through a fixed table (the “runtime ABI”). These are string, Bytes, File, MMap, and the std.* modules that talk to the operating system. You can see the table at src/expression.b.
• The rest are written into the compiler’s own type checker and turned into machine code by the code generator. These are the generic types (List, Map, Box, Atomic, RawPtr, Slice, SIMD) and compile-time helpers like size_of. You can see the checker at src/expression.b.

The current release reports runtime ABI 23, compiler 0.1.53, and the candidate language contract 1.0. Installed release output is shown under Verify the install.

Error handling is builtin

Beans has no null and no exceptions. Instead it gives you three builtin types for “maybe” and “failed” answers, and you will see them all over this reference:

• Option<T>: a value that may be missing.
• Result<T, E>: a value or an error.
• Error: the standard error class.

These, and the collection types like List and Map, are all builtin. Read Option, Result, and Error for the full story.

All builtin pages

Page	What it covers
Primitive types	unit, bool, the integer and float types, byte, string
Numbers and decimal	number rules, casts with as, and exact decimal math
string	the string type and every method on it
Bytes	the growable byte buffer Bytes
Collections	List, Map, and OrderedMap
Option, Result, and Error	Option, Result, Error, some/none/ok/err, the ? operator
Ownership handles	Box, Arena, Shared, Weak, Mutex, Channel, Thread, Brew, TaskGroup, Gate, AtomicInt
Atomics	Atomic<T> and MemoryOrder
Files and mapping	File, Dir, MMap
SIMD, arrays, and pointers	Simd{N}{elem}, [T; N], Slice<T>, RawPtr<T>
Prelude functions	panic, size_of/align_of/offset_of, printing

See also

• The language guide explains how types, errors, memory, and the rest fit together.
• The standard library reference covers the modules you import with import std.*.