Reference

Language reference

The normative text is spec/. This is the working summary.

Declarations

Form	Means
`fn name(args) -> T ! E / {row}`	A function. Return, failure and effects are all part of the type.
`type N = { f: T }`	A struct.
`type N = \| A \| B(v: T)`	A sum, with or without payloads.
`type N[T] = …`	A generic type: a family, one member per use.
`type N = T`	An alias.
`effect N { fn op() -> T }`	An effect and its operations.
`import path`	Brings a module in.
`pub`	Exports a declaration from its module.
`extern fn c_name(...)`	A C function. Calling it performs `unsafe`.
`test "name" { }`	A test, beside the code.
`bench "name" { }`	A benchmark.

Operator	On
`+ - * / %`	`i64` and `f64`. `+` also concatenates a `str` or a list.
`^`	Exponentiation — not bitwise xor. A negative integer exponent panics; write it in floats.
`== !=`	Any two values of one type, structurally.
`< <= > >=`	`i64`, `f64`, `str`, and tuples whose every component is ordered.
`and or not`	Booleans. `and` and `or` short-circuit.
`??`	Opens an `Option` or a fallible with a default. The right side is lazy.
`\|>`	Pipes a value into a call.
`..` `..=`	A range, exclusive or inclusive.

Interpolation is "{expr}", and the expression inside needs no escaping for its own quotes. len() counts characters; byte_len() counts bytes.

254 numbered clauses across spec/, each with a conformance program that runs in the test suite. More on the specification.