• Only one non-terminal at the left hand side,

  • What is type 3 grammar? Explain its properties



    Type 3 grammars are regular grammars that describe regular / formal languages.

    These grammars contain production rules consisting of the following −

    • Only one non-terminal at the left hand side,

    • The right hand side has a single terminal and may or may not be followed by non terminals.

    Example

    A → ε , A → a, A → b, A → aA etc.

    Types

    There are two types of regular grammars namely −

    • Right linear / Right regular grammar

    • Left linear / Left regular grammar

    Let us learn about these two types of grammar in detail.

    Right linear grammar

    This is a regular grammar with the production rules of the form

    A → α (or) A → α B

    Where, A, B → non terminal symbols α → terminal symbol

    These grammars are right-branching in nature, since the substitution is done for the right most non terminal, if available.

    Left linear grammar

    This is a regular grammar with the production rules of the form −

    A → α (or) A → B α

    Where, A and B are non terminals and α is a terminal symbol.

    Since the substitution is done for the leftmost non-terminal, these grammars are left branching in nature.

    Properties of Regular grammars

    The regular grammars generates regular languages which are closed under the following −

    • Union

    • Concatenation

    • Intersection

    • Complementation

    • Difference

    • Reversal

    • Reversal

    • Closure

    • Homomorphism

    • Inverse homomorphism.

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