rust/doc/tutorial/intro.md

Introduction

Scope

This is a tutorial for the Rust programming language. It assumes the reader is familiar with the basic concepts of programming, and has programmed in one or more other languages before. The tutorial covers the whole language, though not with the depth and precision of the language reference.

Disclaimer

Rust is a language under development. The general flavor of the language has settled, but details will continue to change as it is further refined. Nothing in this tutorial is final, and though we try to keep it updated, it is possible that the text occasionally does not reflect the actual state of the language.

First Impressions

Though syntax is something you get used to, an initial encounter with a language can be made easier if the notation looks familiar. Rust is a curly-brace language in the tradition of C, C++, and JavaScript.

fn fac(n: int) -> int {
    let result = 1, i = 1;
    while i <= n {
        result *= i;
        i += 1;
    }
    ret result;
}

Several differences from C stand out. Types do not come before, but after variable names (preceded by a colon). In local variables (introduced with let), they are optional, and will be inferred when left off. Constructs like while and if do not require parenthesis around the condition (though they allow them). Also, there's a tendency towards aggressive abbreviation in the keywords—fn for function, ret for return.

You should, however, not conclude that Rust is simply an evolution of C. As will become clear in the rest of this tutorial, it goes in quite a different direction.

Conventions

Throughout the tutorial, words that indicate language keywords or identifiers defined in the example code are displayed in code font.

Code snippets are indented, and also shown in a monospace font. Not all snippets constitute whole programs. For brevity, we'll often show fragments of programs that don't compile on their own. To try them out, you might have to wrap them in fn main() { ... }, and make sure they don't contain references to things that aren't actually defined.