23. Reserved Words

Because a type only ever appears in bars (|box|) and an id always wears a #, type names are free as ids and ids are free as type names — |block#oval| is fine, and block -> oval is two ordinary nodes. A small set of words stays reserved:

• node, link, and the structural class names text, marker, canvas, scene, cut: not instantiable types — node is the umbrella concept (write |block| for the bare box), links are drawn by operators and styled by |-| (|link| is an error), and a define may not take one of these (its generated .lini-<name> would collide with a built-in SVG class — |-| lowers to the reserved .lini-link).

The lini- prefix is reserved for generated names: desugar generates the type classes (.lini-block, .lini-box, .lini-<define>) and mints ids (#lini-topic-N — SPEC 12), so a user class or an authored id may not begin lini-. User classes are emitted .lini-style-<name>. The highlighter’s token classes (.lini-tok-<kind> — SPEC 20) take the same prefix for the same reason: they land in a host’s document, where an unprefixed name would collide.

The side names top, bottom, left, right are not reserved — they are keywords only after an endpoint’s : (a:left), so a node may be named |box#left|. Single quotes (') are reserved and are not strings.

Value keywords are contextual, not reserved as ids — flow, grid, stack, tree, sequence, chart, pie, drawing, floorplan, schematic, row, column, radial, bilateral, start, center, end, stretch, evenly, origin, none, auto, orthogonal, natural, straight, px mean their keyword only after the property that expects them. Every built-in type — the primitives (SPEC 7), the templates (SPEC 8), and each layout’s own types (SPEC 13–SPEC 16) — is protected from a define shadowing it, free as an id. Function names rgb, rgba, hsl, repeat are reserved only before ( — as are hatch, grid / radial (in pattern:), and the pen calls (move, left, right, up, down, line, angle, arc, curve, fillet, chamfer, circle, close) inside a draw: value.

In link-operator position the marker glyphs + (one) and o (zero) are contextual — they compose the ER cardinality marker (SPEC 9) and mean nothing elsewhere; o is valid only next to a max glyph (-o<, +o-, …), so it never collides with an id or the round measuring op (o) (delimited by parens). A leading + not followed by a digit starts a cardinality op, mirroring -. The digit 0 is not part of any operator — a round endpoint is marker-end: circle (a larger filled dot, SPEC 7; the hollow ring exists only inside the ER glyphs), never -o.

Inside a (…) expression (SPEC 10.7), pi, e, and the sample parameters u / x are keywords, and the math-function names (sin, exp, min, …) are reserved before ( — all contextual to the expression, free as ids elsewhere. The backtick ` is unused and reserved.