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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 More
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 More
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 More
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 More
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 More
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 More
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 More
To find the missing numbers in a sequence in R data frame column, we can use setdiff function.For Example, if we have a data frame called df that contains a column say X and we want to check which values between 1 to 20 are missing in this column then we can use the below command −setdiff(1:20,df$X)Example 1Following snippet creates a sample data frame −x
To extract columns from an R data frame having at least one non-duplicate, we can use Filter function.For Example, if we have a data frame called df that contains some columns having duplicate values and columns that do not contains at least one non-duplicate then we can extract columns having at least one non-duplicate by using the below command −Filter(var,df)Example 1Following snippet creates a sample data frame −x1
To create bar plot for grouped data in base R, we can create the table for both the columns and then use beside argument of barplot function to create the bar plot. To differentiate between the bars, we need to set legend argument to TRUE as well. To understand how it can be done check out the below Example.ExampleFollowing snippet creates a sample data frame −G