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Computer Programming Articles
Page 8 of 18
What is types of LR Parser in compiler design?
There are three types of LR Parsers which are as follows −Simple LR Parser (SLR) − SLR represents "Simple LR Parser". It is very easy and costeffective to execute. But it fails to make a parsing table for some class of grammars, i.e., why CLR and LALR are used which implements mainly all class or type of grammars. It constructs parsing tables which helps to perform parsing of input strings. SLR Parsing can be done if context-free Grammar will be given. In LR (0), 0 means there is no Look Ahead symbol.The SLR parsing action and goto function from the ...
Read MoreWhat is types of Intermediate Code Representation?
The translation of the source code into the object code for the target machine, a compiler can produce a middle-level language code, which is referred to as intermediate code or intermediate text. There are three types of intermediate code representation are as follows −Postfix NotationIn postfix notation, the operator comes after an operand, i.e., the operator follows an operand.ExamplePostfix Notation for the expression (a+b) * (c+d) is ab + cd +*Postfix Notation for the expression (a*b) - (c+d) is ab* + cd + - .Syntax TreeA tree in which each leaf node describes an operand & each interior node an ...
Read MoreWhat is Postfix Notation?
In postfix notation, the operator appears after the operands, i.e., the operator between operands is taken out & is attached after operands.Example1 − Translate a ∗ d − (b + c) into Postfix form.Solutionad ∗ bc + −Example2 − Convert a + (b ∗⊝ c) is in Postfix form.SolutionHere ⊝ represents the unary minus operator.a b c ⊝ ∗ +Example3 − Convert Postfix Expression into Infix Expression using Stack Implementationa d ∗ bc + −SolutionString SymbolsStackad ∗ bc + −AADad*(a * d)B(a * d)bC(a * d)b c+(a ∗ d)(b + c)-(a ∗ d)-(b + c)Example4 − Calculate the value for ...
Read MoreWhat is Intermediate Code Generation?
Intermediate code can translate the source program into the machine program. Intermediate code is generated because the compiler can’t generate machine code directly in one pass. Therefore, first, it converts the source program into intermediate code, which performs efficient generation of machine code further. The intermediate code can be represented in the form of postfix notation, syntax tree, directed acyclic graph, three address codes, Quadruples, and triples.If it can divide the compiler stages into two parts, i.e., Front end & Back end, then this phase comes in between.Example of Intermediate Code Generation −Three Address Code− These are statements of form ...
Read MoreWhat is Implementation of Syntax Directed Translators?
A syntax-directed translation scheme is a context-free grammar in which attributes are related to the grammar symbol and semantic actions enclosed within braces ({ }). These semantic actions are the subroutines that are known by the parser at the suitable time for translation. The location of the semantic actions on the right side of production denotes the time when it will be known for implementation by the parser.When it can produce a translation scheme, it should provide that an attribute value is available when the action defines it. This needed thatInherited attributes of a symbol on the right side of ...
Read MoreWhat is Types of Syntax Directed Translation Schemes?
There are two types of Syntax directed translation schemes which are as follows −Synthesized TranslationIn this translation, values of variables on L.H.S of a production rule depend on the value of the variable on R.H.S of production rule.For Example, E → E(1) + E(2) {E. VAL = E(1). VAL + E(2). VAL}Here, E on L.H.S of production rule can be computed by the sum of values of E(1) and E(2) which are on R.H.S of a production rule, i.e., L.H.S variable is dependent on R.H.S variables.In synthesized translation, the value of the synthesized attribute at the node is evaluated ...
Read MoreWhat is the Syntax Directed Translation?\\n
In syntax directed translation, along with the grammar it can identify some informal notations and these notations are known as as semantic rules.After implementing the Semantic Analysis, the source program is modified to an intermediate form.There is some information that is required by the Intermediate code generation phase to convert the semantically checked parse tree into intermediate code. But this information or attributes of variables cannot be represented alone by Context- Free Grammar.So, some semantic actions have to be attached with Context-Free grammar which helps the intermediate code generation phase to generate intermediate code.So, Attaching attributes to the variables of ...
Read MoreFind FIRST & FOLLOW for the following Grammar\\nE → E + T|T\\nT → T ∗ F|F\\nF → (E)|id
SolutionComputation of FIRSTE → E + T|TSince FIRST (E) does not contain ε.∴ FIRST (E) = FIRST(E + T) = FIRST(E)As, E → T∴ FIRST (E) = {FIRST(T)} (1)T → T ∗ F|FAs FIRST (T) does not contain ε or T does not derive ε.∴ FIRST (T) = FIRST(T ∗ F) = {FIRST(T)}As, T → F (FIRST(T) = {FIRST(F)} (2)F → (E)|id∴ By Rule (3)of FIRSTFIRST (F) = {(, id} ...
Read MoreWhat is Implementation of LR Parsing Tables?
LR Parsing Tables are a two-dimensional array in which each entry represents an Action or goto entry. A programming language grammar having a large number of productions has a large number of states or items, i.e., I0, I1 … … In.So, due to more states, more Actions & goto entries will be filled, which requires a lot of memory. So, a two-dimensional array is not sufficient to store so many action entries, because each entry requires at least 8 bits to encode.So, we have to use more efficient encoding than a two-dimensional array for encoding, Action & goto field.For example, ...
Read MoreConsider the ambiguous grammar.\\nE → E + E\\nE → E * E\\nE → (E)\\nE → id\\n(a) Construct LR (0) items for above grammar.\\n(b) Construct SLR parsing table for grammar.\\n(c) Parse the input string id + id * id.
Problem Statement Consider the ambiguous grammar.E → E + EE → E * EE → (E)E → id(a) Construct LR (0) items for above grammar.(b) Construct SLR parsing table for grammar.(c) Parse the input string id + id * id. SolutionStep1− Construct Augmented Grammar(0) E′ → S(1) E → E + E(2) E → E ∗ E(3) E → (E)(4) E → idStep2− Find closure & goto functions to construct LR (0) items.Closure (E′ → ∙ E) =Applying goto on I9∵ goto cannot be applied on I9, ...
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