cpe1.c

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

char prog[80];
int progIndex;
char *rwtab[6] = {"begin", "if", "then", "while", "do", "end"};

const int SYN_ERROR = -1;
const int SYN_EXIT = 0;
const int SYN_NUM = 11;
const int SYN_VARIABLE = 10;
const int SYN_PLUS = 13;
const int SYN_MINUS = 14;
const int SYN_MULTIPLY = 15;
const int SYN_DIVISION = 16;
const int SYN_COLON = 17;
const int SYN_COLON_EQ = 18;
const int SYN_LESS = 20;
const int SYN_LESS_GT = 21;
const int SYN_LESS_EQ = 22;
const int SYN_GREATER = 23;
const int SYN_GREATER_EQ = 24;
const int SYN_EQUAL = 25;
const int SYN_SEMICOLON = 26;
const int SYN_LEFT_PARENTHESIS = 27;
const int SYN_RIGHT_PARENTHESIS = 28;

typedef struct ScanResult {
    int syn;
    char token[8];
    int sum;
} ScanResult;

ScanResult makeScanResult(int syn, char *token, int sum) {
    ScanResult result;

    result.syn = syn;
    result.sum = sum;
    strcpy(result.token, token);

    return result;
}

u_int8_t CharIsLetter(char ch) {
    if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z')) {
        return 1;
    } else {
        return 0;
    }
}

u_int8_t CharIsDigit(char ch) {
    if (ch >= '0' && ch <= '9') {
        return 1;
    } else {
        return 0;
    }
}

u_int8_t CharIsDigitOrLetter(char ch) {
    return (u_int8_t) (CharIsDigit(ch) || CharIsLetter(ch));
}

int GetKeywordSyn(char *token) {
    for (int n = 0; n < 6; n++) {
        if (strcmp(token, rwtab[n]) == 0) {
            return n + 1;
        }
    }

    return 0;
}

ScanResult scanner() {
    char token[8], ch;
    int tokenIndex = 0, sum = 0;

    for (int n = 0; n < 8; n++)
        token[n] = 0;

    ch = prog[progIndex++];
    while (ch == ' ' || ch == '\n')
        ch = prog[progIndex++];

    if (ch == 0 || ch == '#') {
        return makeScanResult(SYN_EXIT, "", 0);
    }

    if (CharIsLetter(ch)) {
        while (CharIsDigitOrLetter(ch)) {
            token[tokenIndex++] = ch;
            ch = prog[progIndex++];
        }
        progIndex--;

        int keywordSyn = GetKeywordSyn(token);
        if (keywordSyn == 0) {
            return makeScanResult(SYN_VARIABLE, token, 0);
        } else {
            return makeScanResult(keywordSyn, token, 0);
        }
    }

    if (CharIsDigit(ch)) {
        while (CharIsDigit(ch)) {
            sum = sum * 10 + ch - '0';
            ch = prog[progIndex++];
        }
        progIndex--;
        return makeScanResult(SYN_NUM, "", sum);
    } else {
        switch (ch) {
            case '<':
                tokenIndex = 0;
                token[tokenIndex++] = ch;
                ch = prog[progIndex++];
                if (ch == '>') {
                    token[tokenIndex] = ch;
                    return makeScanResult(SYN_LESS_GT, token, 0);
                } else if (ch == '=') {
                    token[tokenIndex] = ch;
                    return makeScanResult(SYN_LESS_EQ, token, 0);
                } else {
                    progIndex--;
                    return makeScanResult(SYN_LESS, token, 0);
                }
            case '>':
                tokenIndex = 0;
                token[tokenIndex++] = ch;
                ch = prog[progIndex++];
                if (ch == '=') {
                    token[tokenIndex] = ch;
                    return makeScanResult(SYN_GREATER_EQ, token, 0);
                } else {
                    progIndex--;
                    return makeScanResult(SYN_GREATER, token, 0);
                }
            case ':':
                tokenIndex = 0;
                token[tokenIndex++] = ch;
                ch = prog[progIndex++];
                if (ch == '=') {
                    token[tokenIndex] = ch;
                    return makeScanResult(SYN_COLON_EQ, token, 0);
                } else {
                    progIndex--;
                    return makeScanResult(SYN_COLON, token, 0);
                }
            case '+':
                token[0] = ch;
                return makeScanResult(SYN_PLUS, token, 0);
            case '-':
                token[0] = ch;
                return makeScanResult(SYN_MINUS, token, 0);
            case '*':
                token[0] = ch;
                return makeScanResult(SYN_MULTIPLY, token, 0);
            case '/':
                token[0] = ch;
                return makeScanResult(SYN_DIVISION, token, 0);
            case '=':
                token[0] = ch;
                return makeScanResult(SYN_EQUAL, token, 0);
            case ';':
                token[0] = ch;
                return makeScanResult(SYN_SEMICOLON, token, 0);
            case '(':
                token[0] = ch;
                return makeScanResult(SYN_LEFT_PARENTHESIS, token, 0);
            case ')':
                token[0] = ch;
                return makeScanResult(SYN_RIGHT_PARENTHESIS, token, 0);
            default:
                return makeScanResult(SYN_ERROR, "", 0);
        }
    }
}

int main() {
    char ch;

    progIndex = 0;
    printf("Please input string:\n");
    do {
        ch = (char) getchar();
        prog[progIndex++] = ch;
    } while (ch != '#');
    prog[progIndex] = 0;
    progIndex = 0;
    for (;;) {
        ScanResult result = scanner();
        if (result.syn == SYN_EXIT) {
            break;
        }
        switch (result.syn) {
            case SYN_NUM:
                printf("(%2d,%8d)\n", result.syn, result.sum);
                break;
            case SYN_ERROR:
                printf("Input Error\n");
                break;
            default:
                printf("(%2d,%8s)\n", result.syn, result.token);
        }
    }

    return 0;
}