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Difference between top down and bottom up parsing?
Top-down parsing starts with the input and works its way down to the start symbol, while bottom-up parsing starts with the input and works its way up to the start symbol. Top-down parsing uses predictive parsing techniques, such as LL and recursive descent, while bottom-up parsing uses shift-reduce or LR parsing algorithms.
Why stack is preferable data structure for bottom up parsing?
Stacks are not only the preferred data structure for bottom up parsing, they are the only data structure suitable for bottom up parsing. Bottom-up parsing is usually referred to as depth-first search. Top-down parsing is referred to as breadth-first search. The two are exactly the same in terms of implementation, the difference is only in the structure used to store information collated from the previous iterations. With top-down parsing you use a queue, pushing to the back and popping from the front. With bottom-up parsing you use a stack, pushing to and popping from the back.
What is the role of a parser in compiler design?
· In the compiler model, the parser obtains a string of tokens from the lexical analyser, and verifies that the string can be generated by the grammar for the source language.· The parser returns any syntax error for the source language.· There are three general types' parsers for grammars.· Universal parsing methods such as the Cocke-Younger-Kasami algorithm andEarley's algorithm can parse any grammar. These methods are too inefficient to use in production compilers.· The methods commonly used in compilers are classified as either top-down parsing or bottom-up parsing.· Top-down parsers build parse trees from the top (root) to the bottom (leaves).· Bottom-up parsers build parse trees from the leaves and work up to the root.· In both case input to the parser is scanned from left to right, one symbol at a time.· The output of the parser is some representation of the parse tree for the stream of tokens.· There are number of tasks that might be conducted during parsing. Such as;o Collecting information about various tokens into the symbol table.o Performing type checking and other kinds of semantic analysis.o Generating intermediate code.
What is the role of parser in compiler design?
· In the compiler model, the parser obtains a string of tokens from the lexical analyser, and verifies that the string can be generated by the grammar for the source language.· The parser returns any syntax error for the source language.· There are three general types' parsers for grammars.· Universal parsing methods such as the Cocke-Younger-Kasami algorithm andEarley's algorithm can parse any grammar. These methods are too inefficient to use in production compilers.· The methods commonly used in compilers are classified as either top-down parsing or bottom-up parsing.· Top-down parsers build parse trees from the top (root) to the bottom (leaves).· Bottom-up parsers build parse trees from the leaves and work up to the root.· In both case input to the parser is scanned from left to right, one symbol at a time.· The output of the parser is some representation of the parse tree for the stream of tokens.· There are number of tasks that might be conducted during parsing. Such as;o Collecting information about various tokens into the symbol table.o Performing type checking and other kinds of semantic analysis.o Generating intermediate code.
What is the design technique that programer use to breakdown algorithm into modules?
top-down design
The easy logic of Merge sort in C?
Top down merge sort is the easy way of merge sort in C language . It is used to derived o(n log n) algorithm . This is in par with the other methods.
What is a sequential algorithm?
A sequential algorithm has the following characteristics:a dependence on the standard environment,a relevant name,a main method (function/subroutine) with no parameters,supplementary methods using a top-down modular design,input of boolean values,output exemplifying the relevant criteria.
How do you reduce in parsing table for expression grammar in compiler course. i under stand the shift action but unable to understand reduce action please help?
In a parsing table for an expression grammar, the reduce action is used to combine grammar rules to reduce a portion of the input string into a non-terminal symbol. When the parser encounters a reduce action in the parsing table, it replaces a set of symbols on the top of the stack with the non-terminal symbol that corresponds to the grammar rule being applied. This helps in simplifying the input string and moving towards the final goal of parsing the entire input.
A design technique that programmers use to break down an algorithm into modules is known as?
When a programmer breaks down a problem into a series of high-level tasks and continues to break each task into successively more detailed subtasks, this method of algorithm creation is called:
Where do you run an algorithm?
By preparing test cases we can test an algorithm. The algorithm is tested with each test case.
What are geese used for?
Geese have two layers of feathers. One top layer that we see, but beneath they have a layer of down. This down can be used in pillows. Geese can also be used for meat.
Algorithm for implementing push operation on stack?
1. If TOP = MAXSTK THEN [Stack already filled?] Print "OVERFLOW" Go to step 4 Endif 2. TOP = TOP + 1 [Increase TOP by 1] 3. Set ST[STOP] = ITEM [Insert ITEM in new TOP position] 4. End
