What is Parsing? Write down the drawback of top-down parsing of backtracking. - Question & Answer Book

 

Answer: Parsing is the process of analyzing a text, made of a sequence of tokens, to determine its grammatical structure with respect to a given formal grammar. Parsing is also known as syntactic analysis and parser is used for analyzing a text. The task of the parser is essentially to determine if and how the input can be derived from the stat symbol of the grammar The input is a valid input with respect to a given formal grammar if it can be derived from the start symbol of the grammar.

Following are drawbacks of top-down parsing of backtracking:

        i.            Semantic actions cannot be performed while making a prediction. The actions must be delayed until the prediction is known to be a part of a successful parse.

      ii.            Precise error reporting is not possible. A mismatch merely triggers backtracking. A source string is known to be erroneous only after all predictions have failed.