# YAMD

Indentation-based markup language that compiles to HTML via Ruby codegen.

## Syntax

Structure is defined by indentation (tabs). Lines at a given indent level belong to the enclosing directive.

### Directives (line-start only)

| Syntax | Description |
|--------|-------------|
| `#% <ruby code>` | Metadata / Ruby statement. e.g. `#% meta "date", "2025 01 01"` |
| `#! <expr>` | Block wrapper. Evaluates `expr` as a Ruby method call, content is passed as a block. e.g. `#! tag('h1')` |
| `#$ <expr>` | Raw block. Like `#!` but inner lines are passed as a raw string (no YAMD parsing). Used for code blocks. e.g. `#$ code` |
| `#. ` | List item. Must appear inside a `#! list(...)` block |

### Inline constructs

| Syntax | Description |
|--------|-------------|
| `` #`...` `` | Inline code |
| `#{expr}` | Ruby expression interpolation (result converted to string) |
| `#(expr)` | Inline math (AsciiMath, rendered to MathML) |
| `#name(args)` | Method call. e.g. `#link("url")` |
| `#name(args)#{ content }#` | Method call with content block. e.g. `#link("url")#{ click here }#` |
| `##` | Escaped literal `#` |
| `}#` | Closes a `#{` content block |

### Comments

Lines matching `#` followed by nothing or a space (i.e. `#` or `# ...`) are comments and are skipped.

### Available renderer methods

These are defined by `HTMLRenderer` in `exe/yamd`:

| Method | Usage |
|--------|-------|
| `tag(name, **attrs)` | HTML element. `#! tag('h2')` |
| `list(numbering)` | List. numbering: `"-"` (ul), `"1"`, `"a"`, `"A"`, `"i"`, `"I"` (ol). Dot-separated for nested: `"-.1"` |
| `link(url)` | Anchor tag. `#link("https://example.com")#{ text }#` |
| `code(lang: Lang::DEFAULT)` | Code block (used via `#$`). Optional `lang:` for highlighting rules |
| `meta(name, value)` | HTML `<meta>` tag. Used via `#%` |
| `inline_code(text)` | Inline `<code>`. Used via `` #`...` `` |
| `inline_math(text)` | AsciiMath to MathML. Used via `#(...)` |

### Example

```
#% meta "date", "2025 01 01"

#! tag('h1')
	Title

Paragraph text with #`inline code` and #link("https://example.com")#{ a link }#.

#! list('-')
	#. First item
	#. Second item with sub-content
		#$ code
			x = 1
```