编译原理作业

scanner.c

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>

#define NUM_OF_KEYWORDS 7
#define BUFFER_SIZE 1000
#define TOKEN_VALUE_SIZE 20

typedef struct Token{
    int id;
    char value[TOKEN_VALUE_SIZE];
} Token;

enum lexemes {ID = 10, NUM, PLUS = 13, MINUS, MUL, DIVIDE, LE, NE, LT, COLON = 21, COLONE, COMMA, LPARENTHESIS = 27, RPARENTHESIS = 28, WRONG = 100};
char buffer[BUFFER_SIZE];
char *keywords[NUM_OF_KEYWORDS] = {"begin", "end", "if", "then", "else", "while", "do"};
int p = 0;
int line = 0;
int lastIsNumOrID = 2;

void ungetch(int n)
{
	while(n--)
	    p--;
}

int isKeyword(char *s)
{
    int i;
    for(i=0; i<NUM_OF_KEYWORDS; i++)
        if(strcmp(s, keywords[i]) == 0)
            return i+1;
    return 0;
}

/* ??double? */ 
double str2db(char *s)
{
    int sign, signn, n, power, i = 0;
    double result = 0.0;

    sign = isdigit(s[0]) ? 1 : (44-s[i++]);

    while(isdigit(n=s[i++]))
        result = 10.0 * result + (n-'0');
    if(s[i] == '.')
        i++;
    for(power=1; isdigit(n=s[i]); i++){
        result = 10.0 * result + (n-'0');
        power *= 10;
    }
    result /= power;
    if(s[i] == 'e'){
    	signn = isdigit(s[++i]) ? 1 : (44-s[i++]);
    	result *= pow(10, signn * atoi(s+i));
    }
    return sign * result;
}

Token scanner()
{
    Token token;
    char c;
    int id, i = 0;

    while(isspace(c=buffer[p++])){
        if(c == '\n')
            line++;
    }
    if(isalpha(c)){
        token.value[i++] = c;
        while(isalnum(c = buffer[p++]) && c != '\0'){
            token.value[i++] = c;
        }
        ungetch(1);
        token.value[i] = '\0';
        token.id = (id = isKeyword(token.value)) ? id : ID;
        lastIsNumOrID = 1;
        return token;
    }
    else if((lastIsNumOrID == 0 && (c == '+' || c == '-') && (isdigit(buffer[p]))) || isdigit(c)){
        token.value[i++] = c;
        while(isdigit(c=buffer[p++]) && c != '\0')
            token.value[i++] = c;
        if(c == '.'){
            token.value[i++] = c;
            while(isdigit(c=buffer[p++]))
                token.value[i++] = c;
        }
        if(c == 'e'){
            token.value[i++] = c;
            if((c=buffer[p++]) == '+' || c == '-')
                token.value[i++] = c;
            else
                ungetch(1);
            while(isdigit(c=buffer[p++]))
                token.value[i++] = c;
        }
        ungetch(1);
        token.value[i] = '\0';
        token.id = NUM;
        lastIsNumOrID = 1;
        return token;
    }
    else{
        token.value[i++] = c;
        switch(c){
            case '+':
                token.id = PLUS;
                break;
            case '-':
                token.id = MINUS;
                break;
            case '*':
                token.id = MUL;
                break;
            case '/':
                token.id = DIVIDE;
                break;
            case '<':
                if((c = buffer[p++]) == '='){
                    token.id = LE;
                    token.value[i++] = c;
                }
                else if(c == '>'){
                    token.id = NE;
                    token.value[i++] = c;
                }
                else{
                    ungetch(1);
                    token.id = LT;
                }
                break;
            case ':':
                if((c = buffer[p++]) == '='){
                    token.id = COLONE;
                    token.value[i++] = c;
                }
                else{
                    token.id = COLON;
                    ungetch(1);
                }
                break;
            case ';':
                token.id = COMMA;
                break;
            case '(':
            	token.id = LPARENTHESIS;
            	break;
           	case ')':
           		token.id = RPARENTHESIS;
           		break;
            default:
                token.id = WRONG;
                token.value[i++] = line + '0';
        }
        token.value[i] = '\0';
        lastIsNumOrID = 0;
        return token;
    }
}

int main()
{
    char c, fileName[25];
    Token token;
    FILE *fp;

	/* ????ж? */
    do{
    	printf("\nPress i to input codes, or press r to read codes from a file:  ");
    }while((c = getchar()) != 'i' && c != 'r');

	/* ???buffer */
    if(c == 'i'){
	    printf("\nPlease input the codes: (end with #)\n");
    	while((c=getchar()) != '#'){
        	buffer[p++] = c;
    	}
    }
    /* ?ж??buffer */
    else{
    	printf("\nPlease input the file's path: ");
    	scanf("%s", fileName);
    	if((fp = fopen(fileName, "r")) == NULL){
	    	printf("Can't open the file!");
	    	return 1;
	    }
    	while((c=fgetc(fp)) != EOF){
    		buffer[p++] = c;
    	}
    }

	/* ?? */
    while(isspace(buffer[--p]));
   	buffer[p+1] = '\0';
   	getchar();
    p = 0;

	/* scanner()??? */
    while(buffer[p] != '\0'){
        token = scanner();
        if(token.id == NUM){
       		printf("Token is < %d, %e >\n", token.id, str2db(token.value));	
        }   
        else if(token.id == WRONG)
        	printf("Error Found on line %c\n", token.value[1]);
       	else
       		printf("Token is < %d, %s >\n", token.id, token.value);
    }
    /*(+123.456+-456.789e-120)*m2+(a++456)*/
    return 0;
}