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ollama/x/grammar/grammars/README.md

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# Example Grammars
This directory contains example EBNF grammars for constrained decoding.
## Usage
```bash
go run -tags mlx ./x/imagegen/cmd/engine/ \
-model /path/to/model \
-prompt "Your prompt" \
-grammar x/grammar/grammars/json.ebnf \
-grammar-start value
```
## Available Grammars
| File | Start Rule | Description |
|------|------------|-------------|
| `json.ebnf` | `value` | Standard JSON (RFC 8259) |
| `expression.ebnf` | `expr` | Arithmetic expressions (+, -, *, /, parens) |
| `identifier.ebnf` | `ident` | Programming language identifiers |
| `boolean.ebnf` | `expr` | Boolean expressions (AND, OR, NOT) |
| `list.ebnf` | `list` | Comma-separated word list |
| `yesno.ebnf` | `response` | Simple yes/no responses |
| `date.ebnf` | `date` | Dates in YYYY-MM-DD format |
| `email.ebnf` | `email` | Basic email addresses |
| `phone.ebnf` | `phone` | US phone numbers |
| `hexcolor.ebnf` | `color` | CSS hex colors (#RGB or #RRGGBB) |
| `url.ebnf` | `url` | HTTP/HTTPS URLs |
## Grammar Syntax
**Note:** Comments are not supported. Grammar files must contain only EBNF productions.
The grammars use EBNF notation:
- `=` defines a production rule
- `|` is alternation (or)
- `{ }` is repetition (zero or more)
- `[ ]` is optional (zero or one)
- `" "` is a literal string
- `…` is a character range (e.g., `"a" … "z"`)
- `.` ends a production
## Writing Custom Grammars
1. Define your grammar in a `.ebnf` file
2. Choose a start rule name
3. Pass `-grammar path/to/grammar.ebnf -grammar-start rulename`
Example custom grammar for RGB colors:
```ebnf
color = "#" hexdigit hexdigit hexdigit hexdigit hexdigit hexdigit .
hexdigit = "0" "9" | "a" "f" | "A" "F" .
```