Wuffs the Language

The Wuffs project is both a programming language and a standard library written in that programming language (and then e.g. transpiled to C). For more details on the latter, see the Wuffs the Library document. As for Wuffs the Language, it is an imperative C-like memory-safe language that should look roughly familiar to somebody versed in one of C, C++, Go, Java, JavaScript, Rust, etc. The major differentiating features are:

• Facts and compile-time assertions.
• Type refinements.
• Coroutines and an effects system. The ! and ? exclamation and question marks denote impure and coroutine effects.
• No way to dynamically allocate or free memory.

Minor features or restrictions include:

• Nullable and non-nullable pointers, spelled nptr T and ptr T.
• Integrated I/O.
• Iterate loops.
• Public vs private API is marked with the pub and pri keywords. Visibility boundaries are at the package level, unlike C++ or Java's type level.
• No string type, only slices of base.u8. Literals like "#bad checksum" are actually statuses.
• No variable shadowing. All local variables must be declared before any other statements in a function body.
• Like Go, semi-colons can be omitted. Similarly, the () parentheses around an if or while condition are optional, but the {} curly braces are mandatory. There is no ‘dangling else’ ambiguity.
• Labeled jumps look like break.loopname and continue.loopname, for a matching while.loopname.

Wuffs code is formatted by the wuffsfmt program.

Types

Types read from left to right: ptr array[100] base.u32 is a non-null pointer to a 100-element array of unsigned 32-bit integers. Types can also be refined.

Structs

Structs are a list of fields, enclosed in parentheses: struct foo(x: base.u32, y: base.u32), possibly extended with a second list of optionally initialized fields. The struct name, foo, may be followed by a question mark ?, which means that its methods may be coroutines.

Functions

All functions are methods (with an implicit this argument). There are no free-standing functions.

Function definitions read from left to right. func foo.bar(x: base.u32, y: base.u32) base.u32 is a function (a method on the foo struct type) that takes two base.u32s and returns a base.u32. Each argument must be named at the call site. It is m = f.bar(x: 10, y: 20), not m = f.bar(10, 20).

Operators

There is no operator precedence. A bare a * b + c is an invalid expression. You must explicitly write either (a * b) + c or a * (b + c).

Some binary operators (+, *, &, |, ^, and, or) are also associative: (a + b) + c and a + (b + c) are equivalent, and can be spelled a + b + c.

The logical operators, && and || and ! in C, are spelled and and or and not in Wuffs. Not-equals is spelled <>, as the ! exclamation mark is reserved for impure effects.

Expressions involving the standard arithmetic operators (e.g. *, +), will not compile if overflow is possible. Some of these operators have alternative ‘tilde’ forms (e.g. ~mod*, ~sat+) which provide modular and saturating arithmetic. By definition, these never overflow.

The as operator, e.g. x as T, converts an expression x to the type T.

Introductory Example

A simple Wuffs the Language program, unrelated to Wuffs the Library, is discussed in /hello-wuffs-c.