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Basic Definition(s):

Parser: The parser is the phase of the compiler that takes a token string as input and converts it into the corresponding Intermediate Representation (IR) using existing grammar. Syntax Analyzer is another name for the parser.

Abstract Syntax Tree: ASTs (Abstract Syntax Trees) are used to give the compiler a representation of the structure of a program's source code. Typically, a compiler's syntax analysis step produces an AST. It frequently acts as the program's intermediate representation during the several phases the compiler required and has a significant influence on the compiler's final output. Additionally, ASTs are employed in situations like static code analysis. Without actually running the code, automated tools can search through the AST of a program to identify syntax mistakes and problematic patterns.

Left Recursive: Left recursion occurs when the left-most non-terminal in a production of a non-terminal is the non-terminal itself (direct left recursion) or rewrites to the non-terminal through some other non-terminal definitions (indirect left recursion). Take a look at these instances: (1) X -> Xa (direct); (2) X -> Ya; Y -> Xb (indirect).

Basic Definition(s):

PASCAL: Niklaus Wirth created the general-purpose, high-level programming language ‘PASCAL’ in the first half of the 1970s.

LR(0) Parser: One kind of bottom-up parsing is LR parsing. It's employed to parse the broad category of grammars. The "L" in LR parsing refers to input scanning from left to right. The letter "R" signifies for building a right most derivation backwards. The look ahead's "K" input symbol count determines how many parsing decisions will be made. The four components of LR parsing are: LR (0) parsing, SLR parsing, CLR parsing, and LALR parsing. If K is 0, then: (1) An LR(k) parser must decide whether or not to reduce without examining input, which means that no state can have two different reduce actions or a reduce and a shift action; and (2) Without examining input, an LL(k) parser must decide which production of a given non-terminal is applicable. In practice, this means that each non-terminal can only have one production, implying that the language must be finite.

Basic Definition(s):

LR Parser: The "L" stands for input scanning from left to right, and the "R" stands for creating a rightmost derivation in reverse. Almost every programming language construct that can have context-free grammars defined can have an LR parser built to recognize it. Although the LR parsing method is the most often used non-backtracking shift-reduce parsing technique, it can be applied just as effectively as other shift-reduce techniques. The class of grammars that can be properly parsed by LR techniques is a subset of the class that can be properly parsed by predictive parsers. A left-to-right scan of the input by an LR parser can identify a grammatical problem as soon as it is possible.

LL Parser: A one-token look-ahead top-down parser is referred to as an LL(1) parser. The initial L denotes the direction of input reading, which is left to right. It gives a left-to-right derivation, according to the second L. It employs one look-ahead token, according to the 1 as well. Some parsers look forward at the upcoming two tokens or even more.

SLR(1): "Simple LR Parser" stands for it. Execution is incredibly easy and cheap. For some classes of grammars, however, it is unable to create a parsing table, which is why CLR and LALR—which implement the majority of these classes and types of grammars—are utilized. In order to perform input string parsing, it creates parsing tables. The term "SLR(1)" refers to a grammar that uses an SLR parsing table. In the event where context-free grammar is provided, SLR Parsing may be performed.

LR(0): One kind of bottom-up parsing is LR parsing. It's employed to parse the broad category of grammars. The "L" in LR parsing refers to input scanning from left to right. The letter "R" signifies for building a right most derivation backwards. The look ahead's "K" input symbol count determines how many parsing decisions will be made. The four components of LR parsing are: LR (0) parsing, SLR parsing, CLR parsing, and LALR parsing. If K is 0, then: (1) An LR(k) parser must decide whether or not to reduce without examining input, which means that no state can have two different reduce actions or a reduce and a shift action; and (2) Without examining input, an LL(k) parser must decide which production of a given non-terminal is applicable. In practice, this means that each non-terminal can only have one production, implying that the language must be finite.

Basic Definition(s):

LR(1) Parser: To parse the large class of context free grammars, LR parser are used. This method is known as LR(k) parsing. L represents input scanning from left to right. R is used to build a right most derivation in reverse. k is the number of look-ahead input symbols used to make parsing decisions.

Basic Definition(s):

LALR(1) Parser: An LALR(1) parser is a improved version of an LR(0) parser that keeps more precise information in order to disambiguate the grammar. An LR(1) parser is a more powerful parser that stores more precise information than an LALR(1) parser. LALR(1) parsers are always a constant factor greater than LR(0) parsers, and LR(1) parsers are usually exponentially greater than LALR(1) parsers. Any grammar that an LR(0) parser can parse can be parsed by an LALR(1) parser, and any grammar that an LALR(1) parser can parse can be parsed by an LR(1) parser. There are grammars that are LALR(1) but not LR(0), and grammars that are LR(1) but not LALR (1).

LR(1) Parser: To parse the large class of context free grammars, LR parsers are used. This method is known as LR(k) parsing. L represents input scanning from left to right. R is used to build a right most derivation in reverse. k is the number of look-ahead input symbols used to make parsing decisions.

SLR(1) Grammar: "Simple LR Parser" stands for it. Execution is incredibly easy and cheap. For some classes of grammars, however, it is unable to create a parsing table, which is why CLR and LALR—which implement the majority of these classes and types of grammars—are utilized. In order to perform input string parsing, it creates parsing tables. The term "SLR(1)" refers to a grammar that uses an SLR parsing table. In the event where context-free grammar is provided, SLR Parsing may be performed.

LR(1) Grammar: It is common practice to build parsers using LR(1) grammars. These are the LR(1) parser. Almost all context-free programming language constructs can be stated in an LR(1) form. The most versatile grammars that can be parsed by a deterministic, bottom-up parser are LR grammar. A proper superset of the languages that are recognized by predictive (i.e., LL) parsers is described by LR grammars.

Basic Definition(s):

Parser: "One that parses" is a parser. It is a piece of software that separate (deconstruct) text into recognizable character strings for later analysis.

Ambiguous: "Having or expressing more than one conceivable meaning" is what is meant by the word ‘ambiguous’.

Basic Definition(s):

Syntax Analysis: The second stage of a compiler is syntax analysis. It uses data from the lexical analyzer as input. It offers an output that the semantic analyzer can use as input. Syntax analyzer and parser are other names for syntax analysis. It reads the lexical analyzer's string of tokens. Additionally, make sure it can be generated using the source language's grammar.

Type Checking: The compiler performs type checking or static checking at the compiler time. As a result, specific types of programming errors will be identified and reported by compiler. A compiler should ensure that the source program is written using the rules of source language for syntactic and semantic conversions. This type of checking is known as type checking. Apart from it, type checking is a technique for detecting and reporting code errors.

Type Conversions: The term "type conversion" refers to altering the data type of a value. Two strategies exist for doing this: (1) Implicit: The modification is apparent; and (2) Explicit: the modification is made explicitly using a function or operation.

Parsing: "One that parses" is a parser. It is a piece of software that separate (deconstruct) text into recognizable character strings for later analysis.

Basic Definition(s):

Lexical Analyzer: The compiler begins by performing a lexical analysis. It collects updated source code from the language preprocessor that is written as sentences. By removing whitespace from the source code, the lexical analyzer converts these syntaxes into a list of tokens.

FSA: A state machine known as a finite state automaton (FSA) changes its state in response to a string of symbols that are fed into it. A regular expression recognizer is a finite automaton. Finite automata modify their state for each literal when a regular expression string is supplied to them.

Basic Definitions:       

Left Factoring: "Left factoring" denotes a modification in grammar aimed at optimizing it for top-down or predictive parsers. This enhancement addresses scenarios where multiple grammar production rules share a common prefix string, causing ambiguity in the selection of a suitable rule for parsing within a top-down parser. Left factoring serves as a technique to reshape a grammar with a shared prefix, thereby rendering it more conducive for top-down parsers.

Recursive Descent Parser: Recursive-descent parsing is one of the fundamental parsing methods applied in practical applications. These parsers are often referred to as top-down parsers, as they construct parse trees starting from the top and proceeding downwards, as opposed to bottom-up parsers. The core concept of recursive-descent parsing involves associating each non-terminal with a procedure. Each such procedure endeavors to read input characters that the corresponding non-terminal can generate, subsequently relaying this data back to the root of the parse tree for that non-terminal.

Leftmost Derivation: Leftmost derivation encompasses the process of sequentially scanning and substituting the sentential form of an input from left to right.

String: An alphabet is characterized by a finite set of symbols. A string over an alphabet represents a finite sequence of symbols drawn from that specific alphabet. Commonly referred to as words or sentences, strings encapsulate the idea of linguistic constructs. The length of a string denotes the count of symbols (accounting for duplicates) it encompasses. In the context of an alphabet, a language denotes a countable collection of strings over that alphabet.

Basic Definition(s):

Ambiguous String: A sentence (string) from a grammar can easily have more than one production tree, implying that the sentence can be produced in more than one way. An ambiguous string is one that has more than one production tree.

Essential Ambiguous: An ambiguous string (sentence) is spuriously ambiguous if all its production trees (parse trees) describe the same semantics; if some of them differ in their semantics, the ambiguity is essential.

Production Tree: A parse tree is a hierarchical structure that represents the grammar's derivation to obtain input strings. The input is represented concretely by a parse tree. It contains all of the input's information. Parse tree also known as Production tree.

Semantics: The study of meaning in language is known as semantics.

Basic Definition(s):    

Recursive Descent Parser: The Recursive Descent Parser is an upper-to-lower parsing method that builds a parse tree. It initiates from the root and extends to the leaves, utilizing recursive functions to recognize input patterns. It might involve backtracking, a technique of iteratively scanning input to locate the correct parsing path. Predictive parsing is a specific variant of recursive descent parsing that doesn't rely on backtracking. In simple terms, predictive parsing makes parsing decisions without needing to backtrack and re-scan the input. To effectively implement a recursive descent parser, the grammar must meet specific criteria: (1) It must be free from left recursion, where a non-terminal derives itself directly or indirectly; (2) The grammar should be structured in a way that resolves ambiguities and streamlines parsing; (3) The programming language employed should support recursion, allowing functions to call themselves; and (4) In cases where left-factoring isn't feasible, the recursive descent parser can employ backtracking to explore alternative parsing paths.

Predictive Parser: Predictive parsing constitutes a specialized subset within the domain of recursive descent parsers. It denotes a parsing approach where decisions are made based on the prevailing input symbol, dispensing with the need for backtracking. Backtracking involves repetitively scanning input to identify the correct parsing trajectory, a step that predictive parsing circumvents.

Bottom-Up Parser: The Bottom-Up Parser is a parsing technique aimed at constructing a parse tree for a provided input string. It commences parsing from the individual tokens or leaves of the input and progressively constructs more complex structures, ultimately culminating at the root of the parse tree. The primary objective of a bottom-up parser is to deduce the rightmost derivation of the given input string by retracing production rules in reverse order.

Basic Definition(s):

Lexical Analyzer: The compiler begins by performing a lexical analysis. It collects updated source code from the language preprocessor that is written as sentences. By removing whitespace from the source code, the lexical analyzer converts these syntaxes into a list of tokens.

Finite State Automata: A state machine known as a finite state automaton (FSA) changes its state in response to a string of symbols that are fed into it. A regular expression recognizer is a finite automaton. Finite automata modify their state for each literal when a regular expression string is supplied to them.

Regular Description: Regular Expressions (Regular Descriptions) make it easy to explain the language that finite automata can understand. It is the best technique to represent any language. Regular languages are the languages that some regular expressions accept. A series of patterns that define a string can also be used to describe a regular expression.

Transition Table: A tabular representation of the transition function is what the transition table essentially is. The function takes TWO inputs, a STATE and a SYMBOL, and outputs a STATE (that is, the "NEXT STATE"). A transition table is made up of the following elements: (1) Columns represent INPUT SYMBOLS; (2) Rows represent STATES; (3) Entries correspond to the NEXT STATE; (4) START STATE; and (5) FINAL STATE.

Basic Definition(s):

LLgen Parser Generator: With no backtracking from an Extended Context Free grammar, LLgen offers a tool for creating an effective recursive descent parser. LLparse is the name of the parser produced by LLgen.

LL(1) Conflict: LL(1) conflicts are classified into two types: FIRST/FIRST and FIRST/FOLLOW. When the FIRST sets of two different productions for the same non-terminal intersect, a FIRST/FIRST conflict occurs. FIRST/FOLLOW conflict occurs when a grammar rule's FIRST set contains an epsilon and the intersection with its FOLLOW set is not empty.

LR Item Set: A production G with a dot at a specific location on the production's right side is an LR(0) item. It is helpful to utilize LR(0) items to show how much of the input has been scanned up to a specific point in the parsing process.

Basic Definition(s):

FIRST/FIRST Conflict: LL(1) conflicts are classified into two types: FIRST/FIRST and FIRST/FOLLOW. When the FIRST sets of two different productions for the same non-terminal intersect, a FIRST/FIRST conflict occurs. FIRST/FOLLOW conflict occurs when a grammar rule's FIRST set contains an epsilon and the intersection with its FOLLOW set is not empty.

LL(1): A one-token look-ahead top-down parser is referred to as an LL(1) parser. The initial L denotes the direction of input reading, which is left to right. It gives a left-to-right derivation, according to the second L. It employs one look-ahead token, according to the 1 as well. Some parsers look forward at the upcoming two tokens or even more.

Left Factoring: A grammar change called “left factoring” creates a grammar that is better suited for top-down or predictive parser. The top-down parser is unable to decide which grammar production rule to use to parse the given text if many grammar production rules have a common prefix string. Left factoring is the method for transforming a grammar with a common prefix such that top-down parsers will find it useful.

Left Recursion: Left recursion occurs when the left-most non-terminal in a production of a non-terminal is the non-terminal itself (direct left recursion) or rewrites to the non-terminal through some other non-terminal definitions (indirect left recursion). Take a look at these instances: (1) X -> Xa (direct); (2) X -> Ya; Y -> Xb (indirect).

Basic Definition(s):

Sentence: An alphabet is a finite non-empty set A of elements (or vocabulary). Symbols are the alphabet's elements (or letters). A sentence (or word) over A is a set of finite length symbols of A.

Production Tree: A parse tree is a hierarchical structure that represents the grammar's derivation to obtain input strings. The input is represented concretely by a parse tree. It contains all of the input's information. Parse tree also known as Production tree.

Ambiguous: "Having or expressing more than one conceivable meaning" is what is meant by the word ‘ambiguous’.

Parsing: "One that parses" is a parser. It is a piece of software that separate (deconstruct) text into recognizable character strings for later analysis.

Ambiguous String: A sentence (string) from a grammar can easily have more than one production tree, implying that the sentence can be produced in more than one way. An ambiguous string is one that has more than one production tree.

Spuriously Ambiguous: An ambiguous string (sentence) is one that has more than one production tree. A spuriously ambiguous string (sentence) is one in which all of its production trees describe the same semantics.

Semantics: The study of meaning in language is known as semantics.

Basic Definition(s):

Stack: A linear data structure called a stack enforces a specific sequence for the execution of operations. LIFO (Last In First Out) or FILO (First In Last Out) may apply to the order.

Bottom Up Parser: It creates a parse tree for an input string, starting at the leaves and working its way up to the root. Bottom-up parser attempts to find the rightmost derivation of a given string backwards.

FIRST/FIRST Conflict: LL(1) conflicts are classified into two types: FIRST/FIRST and FIRST/FOLLOW. When the FIRST sets of two different productions for the same non-terminal intersect, a FIRST/FIRST conflict occurs. FIRST/FOLLOW conflict occurs when a grammar rule's FIRST set contains an epsilon and the intersection with its FOLLOW set is not empty.

LL(1): A one-token look-ahead top-down parser is referred to as an LL(1) parser. The initial L denotes the direction of input reading, which is left to right. It gives a left-to-right derivation, according to the second L. It employs one look-ahead token, according to the 1 as well. Some parsers look forward at the upcoming two tokens or even more.

Left Factoring: A grammar change called “left factoring” creates a grammar that is better suited for top-down or predictive parser. The top-down parser is unable to decide which grammar production rule to use to parse the given text if many grammar production rules have a common prefix string. Left factoring is the method for transforming a grammar with a common prefix such that top-down parsers will find it useful.

Basic Definition(s):

Parsing: Input analysis, often known as parsing, is the process of organizing data according to grammatical rules.

Semantically Correct: Semantic analysis is the task of ensuring that a program's declarations and statements are semantically correct, that is, that their meaning is clear and consistent with how control structures and data types should be used.

Transition Table: A tabular representation of the transition function is what the transition table essentially is. The function takes TWO inputs, a STATE and a SYMBOL, and outputs a STATE (that is, the "NEXT STATE"). A transition table is made up of the following elements: (1) Columns represent INPUT SYMBOLS; (2) Rows represent STATES; (3) Entries correspond to the NEXT STATE; (4) START STATE; and (5) FINAL STATE.

Basic Definitions:       

Recursive Descent Parser: A Recursive Descent Parser operates in a top-down manner, constructing the parse tree from the root to the leaves. It employs recursive functions to recognize input, and it may or may not involve backtracking. Predictive parsing refers to a subclass of recursive descent parsers that do not rely on backtracking. Backtracking refers to the iterative scanning of input until the correct path is identified. Implementing a recursive descent parser requires the grammar to adhere to certain conditions: (1) It must be devoid of left recursion; (2) Left-factoring is necessary; (3) The language must support recursion; and (4) In cases where the grammar isn't left-factored, backtracking is employed by the recursive descent parser.

Pushdown Automata: A Pushdown Automaton (PDA) refers to a finite automaton that incorporates a stack-based memory.

Code Generation: The code generator component of a compiler transforms intermediate code into target code. It operates during the final phases of the compilation process, following the optimization stages. Typically, the code generator undertakes three tasks in translating optimized intermediate code into target code: (1) Instruction selection; (2) Register allocation; and (3) Instruction ordering. The code generator must ensure that the resulting target code retains the original functionality outlined by the programmer while prioritizing efficiency in terms of both time and space.

Instruction Selection: The goals of instruction selection within code generation include: (1) Ensuring the target machine's instructions are comprehensive and uniform; and (2) Producing high-quality code in terms of speed and size.

Register Allocation: Utilizing registers for operand instructions yields shorter and quicker operations compared to those involving memory operands. Register application entails two sub-problems: (1) Register allocation, which designates the variables residing in registers at specific program points; and (2) Register assignment, determining the particular register housing a variable.

Instruction Ordering: The sequence in which computations are conducted can significantly impact the efficiency of the target code. Certain computation orders necessitate fewer registers for storing intermediate outcomes compared to others.

Basic Definition(s):

Grammar: A grammar is simply a method of describing a language. There are an infinite number of grammars for a particular language. If two grammars describe the same language, they are equivalent. This is especially important when parsing by using top-down parser. While an infinite number of grammars may exist to describe a given language, their parse trees may be very different. An ambiguous grammar is one that can generate two different parse trees for the same sentence (string). Ambiguous grammar is extremely unappealing.

Spuriously Ambiguous: An ambiguous string (sentence) is spuriously ambiguous if all its production trees (parse trees) describe the same semantics; if some of them differ in their semantics, the ambiguity is essential.

Essential Ambiguous: An ambiguous string (sentence) is spuriously ambiguous if all its production trees (parse trees) describe the same semantics; if some of them differ in their semantics, the ambiguity is essential.

LR(1) Parser: One kind of bottom-up parser is LR parser. It's employed to parse the broad category of grammars. The "L" in LR parsing refers to input scanning from left to right. The letter "R" signifies for building a right most derivation backwards.

Basic Definition(s):

LR(1) Parser: To parse the large class of context free grammars, LR parsers are used. This method is known as LR(k) parsing. L represents input scanning from left to right. R is used to build a right most derivation in reverse. k is the number of look-ahead input symbols used to make parsing decisions.

SLR(1) Parser: SLR stands for "Simple LR Parser." Execution is incredibly easy and affordable. However, it is not able to create a parsing table for all classes of grammars, which is why CLR and LALR, which implement the majority of them, are employed. A grammar is considered to be SLR(1) if it has an SLR parsing table.

Subset: If every element in a set A is also an element in a set B, then the set A is a subset of the set B. The set A is therefore contained within the set B.

LALR(1) Parser: An LALR(1) parser is a improved version of an LR(0) parser that keeps more precise information in order to disambiguate the grammar. An LR(1) parser is a more powerful parser that stores more precise information than an LALR(1) parser. LALR(1) parsers are always a constant factor greater than LR(0) parsers, and LR(1) parsers are usually exponentially greater than LALR(1) parsers. Any grammar that an LR(0) parser can parse can be parsed by an LALR(1) parser, and any grammar that an LALR(1) parser can parse can be parsed by an LR(1) parser. There are grammars that are LALR(1) but not LR(0), and grammars that are LR(1) but not LALR (1).

Basic Definitions:       

LR(1) Parser: An LR(1) parser is employed for parsing a broad category of context-free grammars. This parsing approach is known as LR(k) parsing, where "L" signifies scanning input from left to right, "R" pertains to constructing a rightmost derivation in reverse, and "k" represents the count of look-ahead input symbols employed for guiding parsing decisions.

Proportional: The term "proportional" describes a relationship wherein something's size or magnitude is connected in relation to something else.

Cube of the Number: A cube number results from multiplying a number by itself twice. For instance, 8 is a cube number since it is the product of 2 x 2 x 2 (where 2 is multiplied by itself twice). This concept can also be expressed as 2³.

Basic Definitions:       

Shift Reduce Conflict: A Shift-Reduce Conflict constitutes the most prevalent type of conflict detected in grammars. It arises when the grammar allows a rule to be reduced for a specific token while simultaneously permitting another rule to be shifted for that exact same token.

LR(1) Parser: LR parsers are employed to parse a broad range of context-free grammars. This approach is referred to as LR(k) parsing, where "L" indicates scanning input from left to right, "R" is utilized to construct a rightmost derivation in reverse, and "k" signifies the count of look-ahead input symbols employed for guiding parsing decisions.

SLR(1) Parser: "Simple LR Parser" is represented by the acronym SLR. This parser execution is remarkably straightforward and economical. Nevertheless, for certain grammar classes, it might be incapable of constructing a parsing table. This limitation has led to the utilization of CLR and LALR parsers, which cover a broader spectrum of grammar classes and types. SLR(1) parsers generate parsing tables for processing input strings. The term "SLR(1)" pertains to a grammar that utilizes an SLR parsing table. When dealing with a provided context-free grammar, SLR Parsing can be executed.

LR(1) Item: An LR(1) item in the context of a context-free grammar (CFG) G is a sequence in the format A -> [α • β, a]. Here, A -> αβ represents a production in grammar G, and "a" can be either a terminal of G or the special symbol ε.

Basic Definition(s):

Lexical Analysis: The compiler begins by performing a lexical analysis. It collects updated source code from the language preprocessor that is written as sentences. By removing whitespace from the source code, the lexical analyzer converts these syntaxes into a list of tokens.

Nested Parentheses: "Nested" parentheses are parentheses that are inside other parentheses.

Scanner: Software called a scanner converts a string of characters (the program's source file) into a string of tokens that will be fed to the compiler's parser.

Grammar: Programming language syntax is described using grammars. It describes how statements and expressions should be structured.

Basic Definitions:       

LR(0): LR parsing is a type of bottom-up parsing utilized to parse a wide range of grammars. The "L" in LR parsing denotes left-to-right input scanning, while the "R" signifies the creation of a rightmost derivation in reverse. The count of "K" input symbols in the look-ahead determines the number of parsing decisions made. The LR parsing methodology encompasses four components: LR(0) parsing, SLR parsing, CLR parsing, and LALR parsing. When K is set to 0: (1) An LR(k) parser must determine whether to reduce without scrutinizing input, thereby prohibiting any state from having two distinct reduce actions or a reduce and a shift action; and (2) An LL(k) parser must decide the appropriate production of a given non-terminal without analyzing input. Practically, this restricts each non-terminal to a single production, implying finiteness of the language.

SLR(1) Grammar: Abbreviating "Simple LR Parser," SLR(1) grammar is characterized by its straightforward and economical execution. However, for certain grammar classes, it may fail to generate a parsing table, necessitating the employment of CLR and LALR parsers—well-equipped to handle a broader array of grammar classes. SLR(1) parsing tables are constructed to facilitate the parsing of input strings. The label "SLR(1)" is attributed to a grammar utilizing an SLR parsing table. SLR Parsing can be executed when dealing with a provided context-free grammar.

Top-Down Parser: Top-down parsers construct a parse tree for input by commencing at the root and progressively generating nodes in pre-order. Top-down parsing equates to determining the leftmost derivation for an input string.

FIRST Set: FIRST is a grammar-related function pivotal for populating the entries of a transition table. It identifies the set of terminals initiating strings derived from a production rule. Symbol "c" resides within FIRST(α) exclusively if α can transition into "cβ" for some sequence "β" of grammar symbols.

Basic Definition(s):

Hand Written Lexical Analyzer: There are two ways to build a scanner (lexical analyzer). (1) By hand written, beginning with a diagram of how lexemes look, then write code to follow the diagram and return the corresponding token, as well as possibly other information; and (2) feed the patterns describing the lexemes to a "lexer-generator", which then produces the scanner. LEX is the old lexer-generator; FLEX is a more modern one. It should be noted that the speed of the lexical analyzer (not the code generated by the compiler) and error reporting/correction of a hand-written lexical analyzer are typically much better. As a result, the majority of production-level compiler projects develop their own l lexical analyzers.

LEX: The input stream is scanned by a lexical analyzer and creates tokens from character sequences. LEX is a program used to create lexical analyzers.

Basic Definition(s):

Lexical Analyzer: The compiler begins by performing a lexical analysis. It collects updated source code from the language preprocessor that is written as sentences. By removing whitespace from the source code, the lexical analyzer converts these syntaxes into a list of tokens.

Finite State Automata: A state machine known as a finite state automaton (FSA) changes its state in response to a string of symbols that are fed into it. A regular expression recognizer is a finite automaton. Finite automata modify their state for each literal when a regular expression string is supplied to them.

Regular Description: Regular Expressions (Regular Descriptions) make it easy to explain the language that finite automata can understand. It is the best technique to represent any language. Regular languages are the languages that some regular expressions accept. A series of patterns that define a string can also be used to describe a regular expression.

Basic Definitions:       

Parser Generator: A parser generator takes a grammar as input and produces source code capable of parsing sequences of characters based on the provided grammar. The output code creates a parser that can take a string of characters and attempt to match it against the specified grammar.

YACC: YACC, short for "Yet Another Compiler Compiler," operates as both a grammar parser and parser generator. Essentially, it reads a grammar specification and generates code that can organize input tokens into a syntactic tree according to the grammar's rules.

LL(1) Grammar: An LL(1) grammar is a type of context-free grammar that doesn't exhibit multiple entries within its parsing table. The term LL(1) reflects three characteristics: the first "L" signifies left-to-right input scanning, the second "L" denotes leftmost derivation production, and "1" represents making parsing action decisions using just one input symbol of look-ahead at each step.

Bottom-Up Parser: A bottom-up parser constructs a parse tree for an input string by beginning at the leaves and progressively moving upwards to the root. Its primary goal is to identify the rightmost derivation of the provided string in reverse order.

AST (Abstract Syntax Tree): ASTs serve as representations of a program's source code structure within a compiler. Normally, the compiler's syntax analysis phase generates an AST. This structure often functions as the intermediate representation throughout various compiler phases, significantly influencing the final output. Additionally, ASTs are utilized in tasks like static code analysis, enabling automated tools to identify syntax errors and problematic patterns within a program's AST without needing to execute the code.

Preorder: Preorder traversal involves initially visiting the root node, followed by the left sub-tree, and finally, the right sub-tree.

Basic Definitions:       

Left Factoring: "Left factoring" denotes a modification to a grammar that tailors it more effectively for utilization with top-down or predictive parsers. When multiple grammar production rules share a common prefix string, top-down parsers face challenges in determining the appropriate rule for parsing the provided text. Left factoring serves as a technique to restructure such grammars with shared prefixes, making them more suitable for utilization by top-down parsers.

Left Recursion: Left recursion arises when the leftmost non-terminal within a non-terminal's production either directly recurs itself (known as direct left recursion) or reaches the non-terminal through the definitions of other non-terminals (referred to as indirect left recursion). Consider the following instances: (1) X -> Xa (direct left recursion); (2) X -> Ya; Y -> Xb (indirect left recursion).

Left Associative Operators: The order of operator execution, whether left to right or right to left, is determined by associativity. For instance, in the expression x = y = z = 3, the assignment operator functions from right to left. In simpler terms, the value 3 is assigned to z, then z's value is assigned to y, and ultimately, y's value is assigned to x. The parenthesized version of this statement is a = (b = (c = 8)). Left associative operators with the same precedence are evaluated from left to right. For example, operators like addition and subtraction, sharing equal precedence, are evaluated in a left-to-right manner.

Basic Definition(s):

Top-Down Parser: Top-down parsers build a parse tree for the input by starting at the root and creating nodes in pre-order. Top-down parsing is equivalent to finding the leftmost derivation for an input string.

Attribute Grammar: A special type of context-free grammar called attribute grammar adds some extra information (attributes) to one or more of its non-terminals in order to offer context-sensitive information. With values like integer, float, character, string, and expressions, each property has a clearly defined range of possibilities. The context-free grammar can be given semantics through attribute grammar, which can also help define the syntax and semantics of a programming language. The nodes of a tree can communicate values or information using attribute grammar (when viewed as a parse-tree).

AST: ASTs (Abstract Syntax Trees) are used to give the compiler a representation of the structure of a program's source code. Typically, a compiler's syntax analysis step produces an AST. It frequently acts as the program's intermediate representation during the several phases the compiler required and has a significant influence on the compiler's final output. Additionally, ASTs are employed in situations like static code analysis. Without actually running the code, automated tools can search through the AST of a program to identify syntax mistakes and problematic patterns.

Basic Definition(s):

Compiler: A compiler stands as a specialized software application aimed at translating source code from one programming language into another, often into machine language or machine code. This translation empowers processors, including logic chips, to comprehend and execute the provided code.

Code Optimization: Code optimization involves the strategic modification of code to amplify its efficiency and quality. These modifications might address diverse facets, such as shrinking code size, minimizing memory usage, boosting execution speed, and reducing input/output operations.

Preprocessor: A preprocessor assumes the role of a program that conducts operations on source files before the actual compilation process takes place.

Syntactic Analysis: Syntactic analysis, synonymous with parsing, constitutes the subsequent phase following lexical analysis. This stage involves scrutinizing the structural syntax of the input to ensure its adherence to the accurate syntax of the pertinent programming language.

Semantic Analysis: Semantic analysis is tasked with verifying the accuracy of a program's declarations and statements, affirming their intended meaning. This verification encompasses confirming the proper utilization of control structures and data types, thereby upholding overall clarity and consistency.