Source files and declarations

Spaces delimit indented suites. Tabs are rejected, and indentation must return to an existing level. Blank lines and comment-only lines do not affect indentation. Parentheses permit multiline expressions. Comments start with #.

Identifiers contain ASCII letters, digits, and underscores and cannot start with a digit. Keywords and names beginning __plenty_ are reserved. Diagnostics use one-based line and column positions.

Strings accept single, double, or triple quotes; triple quotes permit physical newlines. The first standalone string in an indented function body is its documentation. Use return "text" when that first string should be the returned value. A b prefix makes a byte literal, b"...", which holds ASCII characters and \xHH escapes. Strings accept the escapes \0, \n, \r, \t, \\, \', \", and \u{H...} for a scalar by code point. Integer literals are decimal, hexadecimal (0xFF), octal (0o17), or binary (0b1010), with optional _ digit separators and width suffixes.

Module scope contains functions, classes, enums, protocols, type aliases, constants, static assertions, imports, and target conditionals. Executable statements and mutable bindings belong inside functions; there are no global variables. Named functions belong at module scope; classes and enums can declare methods, and protocols declare method requirements. Anonymous functions can appear in function bodies; see functions.

A line holding only @name annotates the declaration below it. The set of annotations is closed and compiler-known: @copy and @newtype on classes, and @redacted on classes and enums. See annotations.

Names follow lexical scope and prelude rules. Modules use explicit imports, with visibility controlled by pub. An application has a main entrypoint.

Keywords

A keyword cannot name a binding, parameter, field, function, type, or module. These keywords have a meaning in Plenty:

and, as, break, case, class, const, continue, def, dimension, elif, else, enum, export, extern, False, for, from, if, import, in, match, mut, not, opaque, or, pass, protocol, pub, return, True, type, while, with, yield

These are reserved but have no meaning, so a Python or Rust habit is rejected instead of becoming a name:

async, await, lambda, None, struct, trait, try

None, try, and lambda have diagnostics that name the replacement: Nothing, a Result, and an anonymous function. self and is are not keywords. except, finally, and raise are not reserved either, but a statement that begins like Python exception handling is rejected.