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Lexical structure

This page describes how Spine source text is broken into tokens: whitespace, comments, identifiers, literals, and punctuation.

Line terminators and whitespace​

Whitespace (spaces, tabs, unicode spaces, vertical tab, form feed) and line terminators (\n, \r) separate tokens. They have no meaning beyond separating tokens.

Comments​

  • Line comment: from // to the end of the line (the line break is not part of the comment).
  • Block comment: /* … */. Block comments do not nest.

Identifiers​

  • Start with a Unicode alphabetic character or _.
  • Continue with Unicode letters, digits, or _.
  • Version suffix: optional @ immediately followed by one or more ASCII digits, attached to the same identifier token (e.g. Foo@1, prop@42).

If an identifier spells a keyword exactly (case-sensitive), it is treated as that keyword (true, false, namespace, Struct, …).

Numeric literals​

  • Decimal integers: ASCII digits.
  • Decimal floats: optional fractional part, optional exponent (e / E with optional sign). An optional single suffix letter may follow: d D f F b B s S i I l L.
  • Hexadecimal: 0x or 0X plus hex digits (underscores may appear; invalid digit sequences are reported when the file is checked).
  • Octal: 0o or 0O …
  • Binary: 0b or 0B …

A . after a number starts a fractional part only when the following characters fit a numeric literal; otherwise . is member access (e.g. 1.23 vs e.0.foo).

String literals​

  • Double-quoted "…" and single-quoted '…'.
  • Backslash starts an escape sequence. Unterminated strings are invalid.

Regular expression literals​

When / can start a regex literal, the text is read as /pattern/optionalFlags. If that interpretation does not apply, / is the division operator. This distinction matters for expressions such as a / b versus /foo/g.

Boolean literals​

true and false.

Punctuation and operators​

Brackets [](){}, ;, ,, =, ?, :, ., single-character + - * % < > & ^ | ! ~, and multi-character << >> <= >= == != => && || ->. See Operators.

@ for annotations​

A standalone @ begins a field annotation such as @AdminOnly. In name@123, the @123 part is a version on the name, not a separate annotation token.

Invalid characters​

Characters that cannot start a valid token produce a diagnostic when you run dataspine check.