Experiment 1-2 compiling principle lexical analysis program design plan

Experiment 1-2 compiling principle lexical analysis program design plan Experiment 1-2 compiling principle lexical analysis program design plan Experiment 2-3 lexical analyzer Experiment 2-3 "compiling principle" S language analysis program design One, the purpose of the experiment To understand the two design approaches of lexical analyzer: the method of programming directly from the state transition diagram; Use DFA to write generic lexical analysis programs. Second, experimental content Programmatically, according to the state transition diagram Write a lexical analysis program, it from left to right of each character to scanning source program to generate the words one by one binary type, form a binary type (mark) stream file output. Here, the lexical analyzer is used as a single time, as shown in the figure below. Specific tasks include: (1) the input of the organization source program (2) spell out the words and find the number of their categories, form a binary output, and get the word flow file (3) delete comments, Spaces, and unused symbols (4) to find and locate the wrong part of the lexical method and to print the wrong location in the first line of the source program. Output the error message to the screen. (5) for ordinary identifier, and constants, respectively established identifier table (using the linear table storage), and often scales, when faced with an identifier or constant identifiers table lookup or scale, if found, it returns the position, otherwise it returns 0 and fill in the symbol table or scale. Identifier table structure: variable name, type (integer, real, character), assigned data area address Note: the lexical analysis stage only fills in the name of the variable, and the rest is gradually filled in during the analysis, semantic analysis, and code generation. Common scale structure: constant name, constant value Write the DFA simulator Algorithm is as follows: DFA (S = S0, MOVE [], F [], ALPHABET [], ALLS []) / * S for state, initial value for the initial state of DFA, MOVE [] [] as the state transition matrix, F [] for the final set, ALPHABET [] as the ALPHABET, and MOVE in alphabetical order of [] [] column headings in alphabetical order. ALLS [] is a state set * / { Char Wordbuffer [10] = "" / / word buffer empty Nextchar = getchar (); / / read characters I = 0; While (nextchar! = NULL) / / NULL represents these words {if (nextchar!) {ERROR (" illegal character "), return (" illegal "); } S = MOVE [S] [nextchar] / / the next state If (S = NULL) return (" not acceptable "); / / the next state is empty, cannot be identified, and the word is wrong Wordbuffer [I] = nextchar; / / save the word symbol I++; Nextchar = getchar (); } Wordbuffer [I] = '\ 0'; If (S, F) return (wordbuffer); / / to accept The Else return (" not acceptable "); } Requirement: the algorithm to realize DFA algorithm, given a DFA (initial state, the state transition matrix, the final state, the alphabet, state sets), call the DFA (), and identify the words in a given source program and view the results are correct. Third, experimental requirement Can analyze any S language source When you run the lexical analysis program, you should enter the file name of the S source language program that you want to be analyzed in the form of a question and answer form, and then complete the lexical analysis task for the program. Ability to check and handle certain lexical analysis errors The error messages that the lexical analysis program can give include the total number of errors, the line number for each error, the wrong number and the error message. This experiment requires the following two types of errors (number 1, 2) : 1 word of illegal characters: the character does not exist in the table as the illegal character, treatment is to remove the characters, give error messages, "so-and-so illegal" characters. 2: the source program file is over and the comment is not finished. The annotation format is: / *... * / Reserved words and special symbols The word code one 2 3 4 5 6 7 8 9 The word int char float void const The for The if The else then The word mnemonic int char float voidconst The for The if The else then The value of the internal code being used - - - - - - - - - The word code 10 11 12 13 14 15 16 17 18 The word while The switch break The begin The end identifier Numbers (including integers and real Numbers) The word mnemonic while The switch break The begin The end id num The value of the internal code being used - - - - - In the symbol table In the table of constants The word code 19 20 21 22 23 24 25 26 27 The word + - * / % ( ) [ ] The word mnemonic + - * / % ( ) [ ] The value of the internal code being used - - - - - - - - - The word code 28 28 29 30 The word ! = The < > < = > = = ; { } The word mnemonic rlop ; { } The value of the internal code being used ! = The < > < = > = = - - The word code 37 38 39 40 41 42 43 44 45 The word / = + = - = * = % = | | && ! = The word mnemonic / = + = - = * = % = The or The and The not = The value of the internal code being used - - - - - - - - - Word formation rules: The letter = [a-za-z] Number = [0-9] Identifier = (| _) (| number) * Number = number (number) * (.number + | e) Four, S language expressions and statement statements 1. Arithmetic expressions: +, -, *, /, % The relational operator: >, > =, <, = =, = =, = The assignment operator: =, + =, -=, * =, =, % = Variable description: type identifier variable name table; Type identifier: int char float If statement: If expression then statement [else statement] For statements: For (expression 1; expression 2; expression 3) statements While statements: While expressions do statements S language program: functions are composed of functions that cannot be nested. The function format is: Return value function name (parameter) { The data shows that statements } Five, the program reference structure explanation Initscanner function: program initialization: input and open source program files and target program files, initializing the retention word table Scanner function: call the lexscan function to identify the words if the file is not finished. The Lexscan function: determines the call to different word recognition functions based on the first character of the read word Isalpha functions: identify reserved words and identifiers The Isnumber function: identifies the integer, such as the energy, which can be added to recognize part of the real number Isanotation function: handles the division/and comments The Isother function identifies other special characters Output function: Output the binary to the target file, the Output format (the word mnemonic, the word internal code value), such as (int, -) (rlop, >)... Error function: output Error message to screen In addition, you can also set up the symbol table, fill in the symbol form and so on, the student can design by itself. 6, experimental procedure specification Each person completes individually. When finished, the teacher will check in and give the grade. After the experiment is finished, write the experiment report (ask for the writing). The report is as follows: Adult: class, school number, name The name of the experiment: simplify the lexical analyzer The purpose of the experiment is to make a simplified C lexical analyzer by hand, and understand and deeply understand the working principle of compiler lexical analyzer. Three, the experiment content: The reserved words, common identifiers and special symbols in the source file can be distinguished from the reserved words and special symbol tables, and can make simple error handling. ............ Design the lexical analyzer module to call the structure diagram and each module flow chart.Program source code. The execution result of the program: input file, output result file and screen information. Problems and solutions in the experiment. The experience, the opinion, the suggestion. Test source code examples: C / / aa. Void (aa) { Float rate, circle; Rate = 3; Circle rate = 3.14 * * rate; } The output: (1) output file: (void, minus) (id, 0) ((), (), (), (), (). (2) the symbol table for identifiers: Name type address 0 aa one rate 2 circle 3 4 5 (3) table of constants: Name value 0 3 one 3.14 2 3 Experiment site: teach 10 5th floor computer institute soft one room Experiment time: week 5, week 2, unit 6, week 1, 5 units (7:30-9:00 PM) 6