Top-down parsers construct leftmost derivations

State diagrams of the form used for lexical analyzers are representations of a class of mathematical machines called finite automata.

State diagrams of the form used for lexical analyzers are representations of a class of mathematical machines called pushdown automata.

The following grammar is ambiguous

\to   + const | const

The most common bottom-up parser is the recursive-descent parser. 

A recursive-descent parser is a coded version of a syntax analyzer based directly on the BNF description of the syntax of language.

The following grammar is ambiguous

\to   +  | const

The lexical analyzer takes the lexical units from the parser and uses them to construct hierarchical structures called parse trees.

Given the following NFA 

\epsilon -closure ( \{ 3, 8 \} ) is equal to