Found 182 Articles for Programming Languages

A handle is a substring that connects a right-hand side of the production rule in the grammar and whose reduction to the non-terminal on the left-hand side of that grammar rule is a step along with the reverse of a rightmost derivation.Finding Handling at Each StepHandles can be found by the following process −It can scan the input string from left to right until first .> is encountered.It can scan backward until

For terminals a and b in an Operator Grammar we can have the following precedence Relations −a =. b(Equal Precedence) − If R.H.S of production is of form α a β b γ, where β can be ε or single non-terminal then a =. b.Here, α and γ can be any strings.Example − In grammar, S → m A c B e dOn Comparing mAcBed with αaβbγα = mA, a = c, β = B, b = e, γ = dΑAβbγmACBedSo, comparing a with c and b with e we get c =.e.We can also make a different combination for ... Read More

Any string of Grammar can be parsed by using stack implementation, as in shift Reduce parsing. But in operator precedence parsing shifting and reducing is done based on Precedence Relation between symbol at the top of stack & current input symbol of the input string to be parsed.The operator precedence parsing algorithm is as follows −Input − The precedence relations from some operator precedence grammar and an input string of terminals from that grammar.Output − There is no output but it can construct a skeletal parse tree as we parse, with one non-terminal labeling all interior nodes and the use ... Read More

LEADINGIf production is of form A → aα or A → Ba α where B is Non-terminal, and α can be any string, then the first terminal symbol on R.H.S isLeading(A) = {a}If production is of form A → Bα, if a is in LEADING (B), then a will also be in LEADING (A).TRAILINGIf production is of form  A→ αa or A → αaB where B is Non-terminal, and α can be any string then, TRAILING (A) = {a}If production is of form  A → αB. If a is in TRAILING (B), then a will be in TRAILING (A).Algorithm to ... Read More

Operator Precedence Parsing is also a type of Bottom-Up Parsing that can be used to a class of Grammars known as Operator Grammar.A Grammar G is Operator Grammar if it has the following properties −Production should not contain ϵ on its right side.There should not be two adjacent non-terminals at the right side of production.Example1 − Verify whether the following Grammar is operator Grammar or not.E → E A E |(E)|idA → +| − | ∗SolutionNo, it is not an operator Grammar as it does not satisfy property 2 of operator Grammar.As it contains two adjacent Non-terminals on R.H.S of ... Read More

SolutionNFA for the above language will be −Conversion from NFA to DFA −ε − closure(0) = {0, 1, 4} = AFor State AFor input symbol aFor input symbol bFor input symbol c∴ Ta = {2}∴ Tb = {5}Tc = ∅∴ ε − closure (Ta)                       = ε                      − closure (2)= {2} = B∴ ε − closure (Tb)                        = ε                        ... Read More

Deterministic means that on each input there is one and only one state to which the automata can have the transition from its current state. In deterministic finite automata, the head can move only in one direction to scan the input tape symbols. But in the case of two-way, finite automata on scanning an input symbol the head of the tape may move in right or left from its current position.A deterministic finite automata is a set of 5 tuples and defined asM = (Q, Σ, δ, q0, F)Q: A non-empty finite set of states present in the finite control ... Read More

Shift reduce parser is a type of bottom-up parser. It uses a stack to hold grammar symbols. A parser goes on shifting the input symbols onto the stack until a handle comes on the top of the stack. When a handle occurs on the top of the stack, it implements reduction.There are the various steps of Shift Reduce Parsing which are as follows −It uses a stack and an input buffer.Insert $ at the bottom of the stack and the right end of the input string in Input Buffer.Shift: Parser shifts zero or more input symbols onto the stack until ... Read More

Bottom-up parsing can be represented as an attempt to reduce the input string ω to the start symbol of a grammar by discovering out the right-most derivation of ω in reverse. This is similar to generating a parse tree for the input string ω by starting with leaves and proceeding toward the root i.e., attempting to generate the parse tree from the bottom-up.This contains searching for the substring that connect the right side of any of the production of the grammar. This substring is restored by the left-hand side nonterminal of the production if this replacement leads to the generation ... Read More

In top-down parsing, the parse tree is generated from top to bottom, i.e., from root to leaves & expand till all leaves are generated.It generates the parse tree containing root as the starting symbol of the Grammar. It starts derivation from the start symbol of Grammar & performs leftmost derivation at each step.Drawback of Top-Down ParsingTop-down parsing tries to identify the left-most derivation for an input string ω which is similar to generating a parse tree for the input string ω that starts from the root and produce the nodes in a pre-defined order.The reason that top-down parsing follow the ... Read More