图灵机的 C 语言实现

Question

我正在为形式语言理论课程学习图灵机，教授建议运行以下算法 详细查看“TM”背后的逻辑，但不起作用，当尝试编译时告诉我以下错误。

C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c||In function `Tape* insert_tape(Tape*, Direction, char)':|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c|44|error: invalid conversion from `void*' to `Tape*'|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c||In function `Tape* create_tape(char*)':|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c|68|error: invalid conversion from `void*' to `Tape*'|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c||In function `Transition* get_transition(char*)':|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c|80|error: invalid conversion from `void*' to `Transition*'|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c||In function `List* insert_list(List*, char*)':|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c|93|error: invalid conversion from `void*' to `List*'|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c||In function `List* insert_list_transition(List*, Transition*)':|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c|105|error: invalid conversion from `void*' to `List*'|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c||In function `TM* createTM(char*)':|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c|166|error: invalid conversion from `void*' to `TM*'|
C:\Documents and Settings\Melkhiah.EQUIPO01\Mis documentos\Downloads\Tarea3 Discretas\TM.c|167|error: invalid conversion from `void*' to `List*'|
||=== Build finished: 7 errors, 0 warnings ===|

这是代码：

/* This C file implements a Non-determinitic Pushdown Automata
 * author: Kevin Zhou
 * Computer Science and Electronics
 * University of Bristol
 * Date: 21st April 2010
 */
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

typedef struct tapes {
    struct tapes *left;
    struct tapes *right;
    char content;
} Tape;

typedef enum { LEFT,RIGHT } Direction;

typedef struct transition {
    char current_state;
    char tape_symbol;
    char new_state;
    char new_tape_symbol;
    Direction dir;
} Transition;

typedef struct list {
    Transition *content;
    struct list *next;
} List;

typedef struct tm {
    char *input_alpha;
    char *input;
    char *tape_alpha;
    char start;
    char accept;
    char reject;
    List *transition;
} TM;

Tape *insert_tape(Tape *t, Direction dir, char c) {
    Tape *head = t;
    Tape *new1 = calloc(1,sizeof(Tape));;
    new1 -> content = c;
    if(dir == LEFT) {
        while(t->left != NULL) {
            t = t->left;
        }
        new1->right = t;
        new1->left = NULL;
        t->left = new1;
        return new1;
    }
    if(dir == RIGHT) {
        while(t->right != NULL) {
            t = t->right;
        }
        new1->left = t;
        new1->right = NULL;
        t->right = new1;
    }
    return head;
}

Tape *create_tape(char *input) {
    int i=1;
    Tape *t = calloc(1,sizeof(Tape));
    t->content = input[0];
    while(1) {
        if(input[i] == '\0') break;
        t = insert_tape(t,RIGHT,input[i]);
        i++;
    }
    return t;
}

/* turn the input string into Transition fields */
Transition *get_transition(char *s) {
    Transition *t = calloc(1,sizeof(Transition));
    Direction dir;
    t->current_state = s[0];
    t->tape_symbol = s[1];
    t->new_state = s[2];
    t->new_tape_symbol = s[3];
    dir = (s[4]=='R')? RIGHT:LEFT;
    t->dir = dir;
    return t;
}

/* turn the string into transitions and add into list */
List *insert_list( List *l, char *elem ) {
    List *t = calloc(1,sizeof(List));
    List *head = l;
    while(l->next!=NULL)
        l = l->next;
    t->content = get_transition(elem);
    t->next = NULL;
    l->next = t;
    return head;
}

/* insert a transition into a list */
List *insert_list_transition( List *l, Transition *tr) {
    List *t = calloc(1,sizeof(List));
    List *head = l;
    while(l->next!=NULL)
        l = l->next;
    t->content = tr;
    t->next = NULL;
    l->next = t;
    return head;
}

void print_tape( Tape *t,char blank) {
    char c;
    while(1) {
        if(t->content != blank) break;
        t= t->right;
    }
    while(1) {
        if(t==NULL) break;
        c = t->content;
        if(t->content != blank)
            putchar(c);
        t= t->right;
    }
    putchar('\n');
}

void print_transition (Transition *t) {
    char s1[] = "Left";
    char s2[] = "Right";
    if(t==NULL) {
        printf("NULL Transfer");
        return;
    }
    printf("current:%c tape:%c new state:%c new tape:%c direction %s\n",t->current_state,t->tape_symbol,t->new_state,t->new_tape_symbol,(t->dir == LEFT)?s1:s2);
}

/*test if the char c is in the string s */
int contains ( char c, char *s ) {
    int i=0;
    while(1) {
        if(c== s[i]) return 1;
        if(s[i] == '\0') return 0;
        i++;
    }
}

/* test if the input is a valid input */
int is_valid_input( char *input_alpha, char *input ) {
    int i=0;
    char c;
    while(1) {
        c = input[i];
        if(c == '\0') break;
        if(!contains(c,input_alpha)) return 0;
        i++;
    }
    return 1;
}

TM *createTM (char *input) {

    TM *m = calloc(1,sizeof(TM));
    List *tr = calloc(1,sizeof(List));
    char *buffer;
    /*read input alphabet of PDA*/
    buffer = strtok(input,":");
    if(buffer == NULL) {
        printf("Error in reading input alphabet!\n");
        exit(1);
    }
    m->input_alpha = buffer;

    /*read tape alphabet*/
    buffer = strtok(NULL,":");

    if(buffer == NULL) {
        printf("Error in reading tape alphabet!\n");
        exit(1);
    }
    m->tape_alpha = buffer;

    /*read input sequence*/
    buffer = strtok(NULL,":");
    if(buffer == NULL) {
        printf("Error in reading input sequence!\n");
        exit(1);
    }

    if(!is_valid_input(m->input_alpha,buffer)) {
        printf("Error! Input contains some invalid characters that don't match the input alphabet!\n");
        exit(1);
    }

    m->input = buffer;
    buffer = strtok(NULL,":");
    m->start = buffer[0];
    buffer = strtok(NULL,":");
    m->accept = buffer[0];
    buffer = strtok(NULL,":");
    m->reject = buffer[0];

    /*read tape transition*/
    while(1) {
        buffer = strtok(NULL,":");
        if(buffer == NULL) break;
        tr = insert_list(tr,buffer);
    }

    m->transition = tr->next;
    return m;
}

Transition *find_transition(List * list,char state, char tape_symbol) {
    Transition *t;
    while(1) {
        if(list==NULL) return NULL;
        t = list -> content;
        if(t->current_state == state && t->tape_symbol == tape_symbol)
            return t;
        list = list->next;
    }
}

Tape *move(Tape *t,Direction dir, char blank) {
    if(dir == LEFT) {
        if(t->left==NULL) {
            t = insert_tape(t,LEFT,blank);
        }
        return t->left;
    }
    if(dir == RIGHT) {
        if(t->right==NULL) {
            t = insert_tape(t,RIGHT,blank);
        }
        return t->right;
    }
    return NULL;
}

void simulate( TM *m ) {
    /* first symbol in input symbol used to represent the blank symbol */
    const char blank = m->tape_alpha[0];
    char current_state = m->start;
    Tape *tape = create_tape(m->input);
    Tape *current_tape = tape;
    char current_tape_symbol;
    Transition *current_transition;
    while(1) {
        if(current_state == m->accept) {
            printf("Accept\n");
            print_tape(tape,blank);
            break;
        }
        if(current_state == m->reject) {
            printf("Reject\n");
            print_tape(tape,blank);
            break;
        }
        current_tape_symbol = (current_tape==NULL||current_tape ->content == '\0')?blank:current_tape->content;
        current_transition = find_transition(m->transition,current_state,current_tape_symbol);
        current_state = current_transition -> new_state;
        current_tape -> content = current_transition -> new_tape_symbol;
        current_tape = move( current_tape, current_transition ->dir, blank);
    }
}

int main(void) {
    char s[300];
    TM *p;
    scanf("%s",s);
    p = createTM(s);
    simulate(p);
    return 0;
}

为什么这个程序不起作用？

Answer 1

提供的程序是用 C 编写的，但是您正在使用 C++ 编译器进行编译。

使用C再次编译，应该就可以了。

Answer 2

该代码被视为 C++，因为文件扩展名为 .cpp。将其更改为 .c 就可以了。这比开始修改源代码以使其与 C++ 兼容要容易得多（并且不太可能导致问题）。

编辑：我假设使用的编译器是gcc或cl，它们确实根据文件检测语言扩大。由于情况并非如此，您必须告诉我们您正在使用什么编译器（和选项）。

编辑2：为了让它与C++编译器一起工作，您必须将new重命名为new1，就像@whitelionV建议的那样，将所有 calloc() 返回值转换为适当的类型，如下所示：

44     Tape *new1 = (Tape*)calloc(1,sizeof(Tape));;
68     Tape *t = (Tape *)calloc(1,sizeof(Tape));
80     Transition *t = (Transition *)calloc(1,sizeof(Transition));
93     List *t = (List *)calloc(1,sizeof(List));
105    List *t = (List *)calloc(1,sizeof(List));
166    TM *m = (TM *)calloc(1,sizeof(TM));
167    List *tr = (List *)calloc(1,sizeof(List));

Answer 3

new是C++中的保留字，将变量名改为new1之类的。或者将文件名中的 .cpp 更改为 c。