is used throughout the parser to organize compiler front ends. A grammar naturally “Grammar describes the hierarchical structure of most programming language constructs such as the Pascal Language. For example, an if- else statement in Pascal language can have the form If (expression) statement else statement. That is, an if-else statement is the concatenation of the keyword if , an opening parenthesis, an expression, a closing parenthesis, a statement, the keyword else, and another statement. Using the variable to denote an expression and variable to denote a statement, this structuring rule expr stmt can be expressed as: if (expr) else stmt stmt stmt in which the arrow may be read as can have the form” Such a rule is called a production. In “ production, lexical elements like the keyword and the parentheses are called Variables if terminals. like and represent sequence of terminals and called non-terminals” [6]. expr stmt Parser (Syntax Analysis) Design Parsing is the process of determining if a string of tokens can be generated by a grammar. To parse Pascal, it is sufficient to make a single left to right scan over the input, looking ahead one token at a time. Top-Down parsing constructs the nodes of a parse tree starting at the root and proceeding towards the leaves such as the simple example in Figure 8. To construct the parse tree, start at the root and repeatedly do the following two steps:
“Grammar is used throughout the parser to organize compiler front ends. A grammar naturally describes the hierarchical structure of most programming language constructs such as the Pascal Language. For example, an if- else statement in Pascal language can have the form If (expression) statement else statement. That is, an if-else statement is the concatenation of the keyword if , an opening parenthesis, an expression, a closing parenthesis, a statement, the keyword else, and another statement. Using the variable expr to denote an expression and variable stmt to denote a statement, this structuring rule can be expressed as: stmt if (expr) stmt else stmt in which the arrow may be read as “ can have the form” Such a rule is called a production. In production, lexical elements like the keyword if and the parentheses are called terminals. Variables like expr and stmt represent sequence of terminals and called non-terminals” [6]. Parser (Syntax Analysis) Design Parsing is the process of determining if a string of tokens can be generated by a grammar. To parse Pascal, it is sufficient to make a single left to right scan over the input, looking ahead one token at a time. Top-Down parsing constructs the nodes of a parse tree starting at the root and proceeding towards the leaves such as the simple example in Figure 8. To construct the parse tree, start at the root and repeatedly do the following two steps:
DCSPMCompilerV8a.docx