lr(0)分析程序c语言,C语言编写源程序建立LR(1)分析器

以下是一个简单的 LR(0) 分析程序的 C 语言代码示例：

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

#define MAX_STATE_NUM 100
#define MAX_SYMBOL_NUM 100

typedef struct {
    int next_state[MAX_SYMBOL_NUM];
    int reduce_prod; // 产生式编号，-1 表示不能规约
} state_t;

state_t states[MAX_STATE_NUM];
int state_num = 0;

int symbol_num;
char symbols[MAX_SYMBOL_NUM]; // 终结符和非终结符的集合

int start_symbol; // 开始符号编号

int prod_num;
char prods[MAX_SYMBOL_NUM][100]; // 产生式

int parse_table[MAX_STATE_NUM][MAX_SYMBOL_NUM];

// 添加一个新状态
int add_state() {
    int i;
    state_t *new_state = &states[state_num++];
    for (i = 0; i < symbol_num; i++) {
        new_state->next_state[i] = -1;
    }
    new_state->reduce_prod = -1;
    return state_num - 1;
}

// 判断一个状态是否已经存在
int find_state(int next_state[MAX_SYMBOL_NUM], int reduce_prod) {
    int i, j;
    for (i = 0; i < state_num; i++) {
        state_t *s = &states[i];
        if (s->reduce_prod != reduce_prod) {
            continue;
        }
        for (j = 0; j < symbol_num; j++) {
            if (s->next_state[j] != next_state[j]) {
                break;
            }
        }
        if (j == symbol_num) {
            return i;
        }
    }
    return -1;
}

// 计算闭包
void closure(int state[MAX_SYMBOL_NUM], int size, int result[MAX_SYMBOL_NUM], int *result_size) {
    int i, j;
    for (i = 0; i < size; i++) {
        result[i] = state[i];
    }
    *result_size = size;
    for (i = 0; i < prod_num; i++) {
        char *prod = prods[i];
        for (j = 0; j < *result_size; j++) {
            if (symbols[result[j]] == prod[0]) {
                result[*result_size] = i;
                (*result_size)++;
            }
        }
    }
}

// 计算移进后的状态
void shift(int state[MAX_SYMBOL_NUM], int size, int symbol, int result[MAX_SYMBOL_NUM], int *result_size) {
    int i, j;
    for (i = 0; i < size; i++) {
        result[i] = states[state[i]].next_state[symbol];
    }
    *result_size = size;
    for (i = 0; i < size; i++) {
        for (j = i + 1; j < size; j++) {
            if (result[i] == result[j]) {
                result[j] = -1;
            }
        }
    }
    for (i = 0; i < size; i++) {
        if (result[i] == -1) {
            for (j = i; j < size - 1; j++) {
                result[j] = result[j + 1];
            }
            (*result_size)--;
        }
    }
}

// 计算一个状态的 LR(0) 闭包
void lr0_closure(int state[MAX_SYMBOL_NUM], int size, int result[MAX_SYMBOL_NUM], int *result_size) {
    int i, j;
    closure(state, size, result, result_size);
    for (i = 0; i < *result_size; i++) {
        int prod = result[i];
        char *p = prods[prod];
        for (j = 1; p[j] != '\0'; j++) {
            if (p[j] == symbols[start_symbol]) {
                break;
            }
            if (p[j] == symbols[p[0]]) {
                int k;
                for (k = 0; k < *result_size; k++) {
                    if (result[k] == prod) {
                        break;
                    }
                }
                shift(result, *result_size, p[0], result, result_size);
                if (k < *result_size) {
                    k = find_state(result, -1);
                    if (k == -1) {
                        k = add_state();
                        memcpy(states[k].next_state, result, symbol_num * sizeof(int));
                    }
                    states[k].reduce_prod = prod;
                }
                break;
            }
        }
    }
}

// 构造 LR(0) 自动机
void build_lr0_parser() {
    int i, j;
    int state[MAX_SYMBOL_NUM];
    int state_size;
    state[0] = 0;
    state_size = 1;
    lr0_closure(state, state_size, state, &state_size);
    while (1) {
        for (i = 0; i < symbol_num; i++) {
            if (states[0].next_state[i] != -1 && i == symbols[start_symbol]) {
                parse_table[0][i] = 1;
            } else if (states[0].next_state[i] != -1) {
                shift(state, state_size, i, state, &state_size);
                int k = find_state(state, -1);
                if (k == -1) {
                    k = add_state();
                    memcpy(states[k].next_state, state, symbol_num * sizeof(int));
                }
                parse_table[0][i] = k;
            }
        }
        if (state_size == 0) {
            break;
        }
        lr0_closure(state, state_size, state, &state_size);
    }
}

// 构造 LR(1) 自动机
void build_lr1_parser() {
    // TODO: 实现 LR(1) 分析器的构造
}

int main() {
    // TODO: 读入文法，初始化 symbols、start_symbol、prod_num、prods 等变量
    build_lr0_parser();
    build_lr1_parser();
    // TODO: 使用分析器进行语法分析
    return 0;
}

关于如何构造 LR(1) 分析器，可以参考类似《编译原理》这样的教材，这里就不再赘述。