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Computer Programming Articles
Page 12 of 18
What is OPG?
OPG stands for Operator Precedence Grammar. Grammar with the later property is known as operator precedence grammar. It is ε −free Operator Grammar in which precedence relation are disjoint, i.e., If a . > b exists, then b .> a will not exist.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 production E → E A E .We can convert it into ...
Read MoreWhat is Handle?
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
Read MoreWhat are Precedence Relations in Operator Grammar?
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 MoreWhat are LEADING and TRAILING operation of an operator precedence grammar?
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 MoreWhat is Operator Precedence Parsing?
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 MoreConstruct NFA for the following language and convert it into DFA using the algorithm - L = (aa+ (bb*)c*)
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 MoreWhat is Stack Implementation of Shift Reduce Parsing in compiler design?
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 MoreWhat is Ambiguous Grammar?
A Grammar that makes more than one Leftmost Derivation (or Rightmost Derivation) for the similar sentence is called Ambiguous Grammar.Example − Verify whether the following Grammar is Ambiguous or Not.E → E+E|E $\ast$ E|idSolutionFor string id + id * id, there exist two parse trees.E ⇒lm $\underline{E}$+E ⇒ id+ $\underline{E}$⇒ id+$\underline{E}$ $\ast$ E⇒ id+id $\ast$ $\underline{E}$⇒ id+id $\ast$ idE ⇒lm $\underline{E}$ $\ast$ E⇒ $\underline{E}$+E $\ast$ E⇒ id+ $\underline{E}$ $\ast$ E⇒ id+id $\ast$ $\underline{E}$⇒ id+id $\ast$ idSo, the same string is generated using two different leftmost derivations. Each is having a different parse tree.∴ Two different parse trees exist for string id + id ...
Read MoreWhat are Derivations?
Derivations mean replacing a given string’s non-terminal by the right-hand side of the production rule. The sequence of applications of rules that makes the completed string of terminals from the starting symbol is known as derivation.It can derive terminal strings, beginning with the start symbol, by repeatedly replacing a variable with some production. The language of CFG is a set of terminal symbols we can derive so. This language is called context Free Language.Derivations are denoted by ⇒.For example, consider a Grammar.G=({S}, {a, b}, P, S), where, P contains following productions −P={S→aSa |bSb | ∈}In the above, S may be ...
Read MoreWhat is the implementation of a Lexical Analyzer?
Lexical Analysis is the first step of the compiler which reads the source code one character at a time and transforms it into an array of tokens. The token is a meaningful collection of characters in a program. These tokens can be keywords including do, if, while etc. and identifiers including x, num, count, etc. and operator symbols including >, >=, +, etc., and punctuation symbols including parenthesis or commas. The output of the lexical analyzer phase passes to the next phase called syntax analyzer or parser.The syntax analyser or parser is also known as parsing phase. It takes tokens ...
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