Macro polygon 

macro_rules! polygon {
    ($ty:ty, $($line:literal),* $(,)?) => { ... };
}

A macro for visually defining polygons using Unicode characters.

This macro allows you to create polygons by marking vertices with the ● (U+25CF BLACK CIRCLE) character on a 2D grid. Vertices are extracted in reading order (top to bottom, left to right). Each character position represents one unit in the coordinate system, with the origin (0, 0) at the top-left corner.

The macro validates the polygon using Polygon::new, so invalid polygons will panic at runtime.

Syntax

polygon!(Type, "line1", "line2", ...)

• Type: The numeric type for coordinates (e.g., i32, i64, f64)
• Each string literal represents one row of the grid
• ● marks vertex positions
• Other characters (including Unicode box-drawing characters) are ignored

Coordinate System

• X-axis: increases from left to right (column index)
• Y-axis: increases from top to bottom (row index)
• Origin: (0, 0) at top-left

Examples

// Simple triangle
let triangle = rgeometry::polygon!(i32,
    "  ●  ",
    " ● ● "
);
assert_eq!(triangle.iter().count(), 3);

// Pentagon with vertices in CCW order
let pentagon = rgeometry::polygon!(i64,
    "   ●   ",
    "      ●",
    "     ● ",
    " ●     ",
    "●      "
);
assert_eq!(pentagon.iter().count(), 5);

// Triangle with decorative box-drawing characters
let triangle = rgeometry::polygon!(i32,
    "●─────┐",
    "│  ●  │",
    "└────●"
);
assert_eq!(triangle.iter().count(), 3);

Vertex Ordering

Vertices are extracted in reading order (top to bottom, left to right within each row). Place your ● symbols in the order you want them to appear in the polygon boundary.

Panics

This macro will panic at runtime if:

• Fewer than 3 vertices are marked
• The vertices don’t form a simple polygon (self-intersections, etc.)
• The polygon is invalid for any reason Polygon::new would reject