Cheat Sheet

Quick reference for Bear syntax. Click any snippet to copy.

Variables & Constants

Immutable

name := 'Bear'

Mutable

mut count := 0
count += 1

Explicit type

age: int = 25

Constant

const pi = 3.14159

Integers

x: int = 42
y: i64 = 100
z: u8 = 255

Floats

pi: f64 = 3.14
small: f32 = 1.0

Strings

s := 'hello'
name := "world"

Booleans

flag := true
other := false

Arrays

nums := [1, 2, 3]
words := ['a', 'b']

Maps

ages := map[string]int{
    'Alice': 30
}

Basic

fn add(a int, b int) int {
    return a + b
}

No return

fn greet(name string) {
    println('Hello, ${name}')
}

Multiple returns

fn div(a f64, b f64) (f64, bool) {
    if b == 0 { return 0, false }
    return a / b, true
}

Closures

double := fn (x int) int { x * 2 }

If / else

if x > 0 {
    println('positive')
} else {
    println('negative')
}

If expression

status := if age >= 18 { 'adult' } else { 'minor' }

For range

for i in 0 .. 5 {
    println(i)
}

For each

for val in array {
    println(val)
}

Match

match val {
    0 { println('zero') }
    1 { println('one') }
    else { println('other') }
}

Defer

defer { file.close() }

Option

fn find(id int) ?string {
    if id == 1 { return 'Alice' }
    return none
}

Result

fn parse(s string) !int {
    return error('invalid')
}

Or block

val := find(1) or {
    println('not found')
    return
}

Default value

val := risky() or { 0 }

Struct

struct Point {
    x f64
    y f64
}

Mutable fields

struct User {
    name string
mut:
    active bool
}

Method

fn (p Point) distance() f64 {
    return (p.x * p.x + p.y * p.y).sqrt()
}

Mutable method

fn (mut u User) activate() {
    u.active = true
}

Goroutine

go worker(id)

Channel

ch := chan int{cap: 10}
ch <- 42
val := <-ch

Producer/consumer

fn produce(ch chan int) {
    for i in 0 .. 5 { ch <- i }
    close(ch)
}

Select

select {
    case msg := <-ch1 { ... }
    case msg := <-ch2 { ... }
}

Mutex

lock counter {
    counter.val++
}

Import

import os
import net.http
import json

Named import

import mylib { Function }

C interop

fn C.printf(charptr, ...int) int

Flags

#flag -lmylib
fn C.my_func(int) int