4. Syntax Fundamentals

This chapter teaches the core syntax you need before reading the standard library or the larger examples.

Alef programs are plain text files ending in .alef. A program is made of imports, declarations, and statements. The usual entrypoint is main.

fn main() {
    println("hello")
}

Blocks use braces. Statements are newline-oriented, so simple examples do not need semicolons.

Comments

Use // for a line comment.

// This runs when the program starts.
fn main() {
    println("ready")
}

Values

Alef has strings, integers, floats, booleans, arrays, maps, structs, enums, Result, and Option.

let name = "Ada"
let count = 3
let ratio = 0.75
let ready = true

Strings support interpolation with {name}:

let id = "TD-101"
println("ticket {id} loaded")

Bindings

Use let for local bindings.

Bindings can be reassigned when a program needs to move state forward:

let status = "triage"
status = "progress"

Prefer reassignment when the program is modeling an actual state transition. Prefer new names when each value has a distinct meaning.

Functions

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

Typed signatures are available when they clarify the program:

fn label(id: string, title: string) -> string {
    return "{id}: {title}"
}

Functions are called with parentheses:

let text = label("TD-101", "Checkout timeout")
println(text)

Early Returns

fn priority(plan, blocked) {
    if plan == "enterprise" and blocked {
        return "P0"
    }
    return "P2"
}

Operators

Alef supports common arithmetic, comparison, and boolean operators:

let total = subtotal + tax
let retry = attempts < 3
let urgent = priority == "P0" or customer == "enterprise"
let ready = not blocked and assigned

Use == for equality. Use and, or, and not for boolean logic.

Imports

Imports bring standard-library names into scope:

import std.http { json_response }

fn health(request, state) {
    return json_response("{\"ok\":true}")
}

The standard library is documented as part of the public language surface. The private compiler and runtime source are not needed to use these imports.