# Language - (Grammar|Production) Rule

Recursive rules (known as production):

Production are rules for replacing (or rewriting) nonterminal symbols (on the left side of the production) in a string with other nonterminal or terminal symbols (on the right side of the production).

Expression are not production rules. See Language - Expression

## 3 - Syntax

Production rules are simple replacements. For example, the rule

A -> a

replaces A with a.

There can be multiple replacement rules for any given value. For example,

A -> a
A -> b

means that A can be replaced with either:

• a
• or b.

## 4 - Type

Parsing Steps:

1. Antlr - Lexer Rule (Token names): The lexer creates tokens from the lexer rule.
2. Antlr - Parser Rule: Then, the parser creates an AST from the created tokens with the definition of parser rule.