CoScad syntax modes

A pragma on the first code line selects the vocabulary:

!simple    -- ASCII word set only
!glyph     -- glyph set only
(nothing)  -- legacy: both accepted (all existing files unchanged)

The pragma line is blanked, not stripped, so error line numbers stay right.

Available everywhere (any mode)

• |> pipelines and all pipe-stage words (x, y, z, rotx, move, scale, mirror, extrude, revolve, anchor, at, on, cutat, add, cut, isect, hull, mink)
• $ — Haskell-style loose application: every prefix form's shape argument may be $ <rest of expression>. Works after glyph transforms (χ 5 $ a ⊕ b), word transforms (Translate.x 5 $ a * b), and pipe stages (|> cut $ ...)
• lowercase primitive words: xcyl ycyl zcyl cube box sphere cyl tube torus wedge
• numeric bindings (w = 20, r = w / 2) and loft z p z p ... (see docs/2025-07-14-LANGEXTENSION.md)
• anchor words: top bot lft rt fwd bak ctr (+ combos like top+rt)

!simple vocabulary

Transforms (namespace style):

Translate (x, y, z) obj        Translate.x n obj   (.y .z likewise)
Rotate (x, y, z) obj           Rotate.z n obj      (tuple order: x then y then z)
Scale (x, y, z) obj            Scale.x n obj
Mirror (x, y, z) obj           Mirror.x obj        (no number)
Extrude h obj                  Anchor top obj
Revolve deg obj [segs]         (2D profile -> solid of revolution about Y)
Loft z0 p0 z1 p1 ...           (2D profiles -> solid)

Combinators (prefix, two shape args; second may be $):

Hull a b    Union a b    Intersect a b    Minkowski a b    Offset n a

Operators: * union, - difference. Same flat left-assoc precedence as the glyph operators: a - b * c is (a - b) * c — parenthesize when mixing.

Shapes: Sphere r, Cube s, Box x y z, Cylinder r h, Cone r h, Tube ro ri h, Torus rj rm, Wedge x y z, Prismoid x1 y1 x2 y2 h, Circle r, Triangle r, Pentagon r, Bezier x y x y ... (3k+1 points). All centered (BOSL2 family). Note Box is centered, unlike legacy ▬.

Known limits / notes

• Keywords win over identifiers: you can't name a variable exactly Translate (but Translate2, myTranslate are fine — same rule as xcyl today).
• Errors are reported at file:line:col with the offending line quoted; a name that is not defined anywhere is an "undefined variable", names that depend on each other are a "circular dependency" (only the cycle members are listed), and 2D/3D mismatches are compile errors.
• Rotate (x, y, z) composes as Rz . Ry . Rx (OpenSCAD rotate([x,y,z]) order).
• Translate (x,y,z) emits one translate() vs three nested for χψζ chains — same geometry, cleaner scad.

Assembly checking (coscad check foo.assemble)

.assemble files now take the same !simple / !glyph pragma (governs the asm-side expressions; each referenced part file keeps its own pragma), plus:

clearance 0.15        -- required minimum gap in mm (0 = report contacts only)
tolerance 0.00001     -- how far a mating loop may miss and still close (mm [rotation])

fixed poses and mate roll=/gap= values take numeric atoms (literal, binding, -w, (w / 2)); see docs/2025-07-14-LANGEXTENSION.md, "Rigid assembly constraints".

coscad check isolates each part inside the asm expression (all other parts bound to Empty), renders real meshes, splits instances (a mirrored pair = wing#1, wing#2), and for each AABB-close pair:

• exact overlap via OpenSCAD boolean on emitted polyhedra -> OVERLAP + volume
• CGAL instability on coplanar mating faces is detected (stderr+stdout scan), retried with swapped operands, else falls back to a grid-accelerated vertex-to-triangle distance verdict (annotated in the output)
• contact = touching mating faces (< 0.02mm); WARN = gap below clearance Exit code 2 if any pair overlaps (the design has a problem), 0 otherwise; 1 if the check could not run (no asm, a part that fails to render). Distance verdicts are vertex-sampled: exact for vertex-involved closest features; pathological edge-edge-only cases can read slightly high.