top-down parsing

The major problem with top-down parsing is the time wasted in expanding rules that cannot possibly be satisfied by the input.

Some of the parsers that use top-down parsing include:

The simple implementations of parser combinators have some shortcomings, which are common in top-down parsing.

L-attributed grammar : inherited attributes can be evaluated in top-down parsing.

As a result, attribute evaluation in L-attributed grammars can be incorporated conveniently in top-down parsing.

See Top-down parsing and Bottom-up parsing.

Attribute evaluation in S-attributed grammars can be incorporated conveniently in both top-down parsing and bottom-up parsing.

Top-down parsing is a strategy of analyzing unknown data relationships by hypothesizing general parse tree structures and then considering whether the known fundamental structures are compatible with the hypothesis.

Top-down parsing eagerly decides what a construct is much earlier, when it has only scanned the leftmost symbol of that construct and has not yet parsed any of its parts.

The importance of their polynomial algorithm's power to accommodate 'any form of ambiguous CFG' with top-down parsing is vital with respect to the syntax and semantics analysis during natural language processing.

In computer science, top-down parsing is a parsing strategy where one first looks at the highest level of the parse tree and works down the parse tree by using the rewriting rules of a formal grammar.

Simple implementations of top-down parsing do not terminate for left-recursive grammars, and top-down parsing with backtracking may have exponential time complexity with respect to the length of the input for ambiguous CFGs.

An LL parser is a type of parser that does top-down parsing by applying each production rule to the incoming symbols, working from the left-most symbol yielded on a production rule and then proceeding to the next production rule for each non-terminal symbol encountered.