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It is a kind of notation in which each production of Context-Free Grammar is related with a set of semantic rules or actions, and each grammar symbol is related to a set of Attributes. Thus, the grammar and the group of semantic Actions combine to make syntax-directed definitions.The translation may be the generation of intermediate code, object code, or adding the information in symbol table about constructs type. The modern compiler uses the syntax-directed translation that makes the user’s life easy by hiding many implementation details and free the user from having to specify explicitly the order in which semantic ... Read More
A block is a statement containing its own local data declaration. The concept of a block is originated with ALGOL. The block-structured language permits an array with adjustable length. The main feature of blocks is their bracketing structure (begin and end used in ALGOL) in which they can define their data. In 'C' language, the syntax of the block is −{ declaration statements; }where the braces limit the block. The characteristic of a block is its nesting structure. Delimiters mark the starting and end of the block. In 'C' language, the braces { } act as delimiters, while ALGOL ... Read More
To find the column means if some columns are categorical in R data frame, we can follow the below steps −First of all, create a data frame.Then, use numcolwise function from plyr package to find the column means ifsome columns are categorical.Example 1Create the data frameLet’s create a data frame as shown below −Grp
To convert list with varying number of elements into a data frame in R, we can use stri_list2matrix function of stringi package along with as.data.frame function.For Example, if we have a list called LIST that contains varying number of elements then we can convert it into a data frame by using the below mentioned command −as.data.frame(t(stri_list2matrix(LIST)))Example 1Following snippet creates a sample list −List1
To create a column of log(1+x) in data frames stored in R list, we can follow the below steps −First of all, create a list of data frames.Then, use lapply function to create a column of log(1+x) in data frames stored in the list.ExampleCreate the list of data framesUsing data.frame function to create data frames and list function to create the list of those data frames −df1
In stack allocation, it can analyze how the memory is allocated at runtime when a procedure is called & when the value from the procedure is returned.Passing Parameter to Procedure (param x)− When actual parameter x is passed to the procedure, it will be pushed into the stack, i.e., push (x).∴ param(x) refers to push (x) which refers to decrementing of the top pointer from N + 1 to N and x will be pushed onto the stack.∴ The following statements will be executed.top = top – 1*top = x or 0[top] = xHere 0[top] means 0 offsets from the ... Read More
Stack Allocation scheme is the simplest Run-Time Storage Management Technique. The storage is allocated sequentially in the stack beginning at one end. Storage should be freed in the reverse order of allocation so that a block of storage being released is always at the top of the stack.A program consists of data and procedures. On execution of each procedure, some amount of memory is occupied, which has information regarding the procedure, i.e., its actual parameters, number of arguments, return address, return values & local data, etc. That part of memory is the Activation Record of that procedure.Activation RecordAn Activation Record ... Read More
To multiply vector values in sequence with matrix columns in R, we can follow the below steps −First of all, create a matrix.Then, create a vector.After that, use t function for transpose and multiplication sign * to multiply vector values in sequence with matrix columns.ExampleCreate the data frameLet’s create a data frame as shown below −M
Heap allocation is the most flexible allocation scheme. Allocation and deallocation of memory can be done at any time and any place depending upon the user's requirement. Heap allocation is used to allocate memory to the variables dynamically and when the variables are no more used then claim it back.Heap management is specialized in data structure theory. There is generally some time and space overhead associated with heap manager. For efficiency reasons, it may be useful to handle small activation records of a particular size as a special case, as follows −For each size of interest, keep the linked list ... Read More
The stack allocation is a runtime storage management technique. The activation records are pushed and popped as activations begin and end respectively.Storage for the locals in each call of the procedure is contained in the activation record for that call. Thus, locals are bound to fresh storage in each activation, because a new activation record is pushed onto the stack when the call is made.It can be determined the size of the variables at a run time & hence local variables can have different storage locations & different values during various activations. Suppose that the registered top marks the top ... Read More