摘要

问题描述

William 35 25000
Kishore 41 35000
Wallace 37 20000
Bruce 39 15000

1. 要求从文件中读取这些信息，并输出到屏幕上；
2. 为所有工资小于三万的员工涨3000元；
3. 在屏幕上输出薪资调整后的结果；
4. 把调整后的结果保存到原始文件。

William 35 28000
Kishore 41 35000
Wallace 37 23000
Bruce 39 18000

最终代码

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

typedef char String[32];
typedef FILE* File;

typedef struct _Employee {
  String name;
  int age;
  int salary;
  struct _Employee *next;
} *Employee;

typedef void (*Callback)(Employee);

/* High Order Functions  */
void foreach(Employee e, Callback fn) {
  Employee p;
  while (p = e) {
    e = e->next;                /* Avoid *next be changed in fn */
    fn(p);
  }
}

void with_open_file(String filename, String mode, Callback fn, Employee e) {
  File file = freopen(filename, mode, (mode[0] == 'r'? stdin: stdout));
  if (file == NULL) {
    fprintf(stderr, "Cannot open %s with %s mode.\n", filename, mode);
    exit(EXIT_FAILURE);
  }
  fn(e);
  fclose(file);
}

/* Destructor */
static void employee_free_node(Employee e) {
  if (e != NULL) {
    free(e);
  }
}

void employee_free(Employee e) {
  foreach(e, employee_free_node);
}

/* Input */
static void employee_read_node(Employee node) {
  Employee e = NULL, *head = (Employee*) node;
  e = *head = (Employee)calloc(1, sizeof(struct _Employee));
  if (e != NULL && scanf("%s%d%d", e->name, &e->age, &e->salary) != 3) {
    employee_free(e);
    *head = NULL;
  }
}

void employee_read(Employee list) {
  Employee e = NULL, *head = (Employee*) list, tail = NULL;

  *head = NULL;
  while (employee_read_node((Employee)&e), e) {
    if (*head != NULL) {
      tail->next = e;
      tail = e;
    } else {
      *head = tail = e;
    }
  }
}

/* Output */
static void employee_print_node(Employee e) {
  printf("%s %d %d\n", e->name, e->age, e->salary);
}

void employee_print(Employee e) {
  foreach(e, employee_print_node);
}

/* Business Logic */
static void employee_adjust_salary_node(Employee e) {
  if (e->salary < 30000) {
    e->salary += 3000;
  }
}

void employee_adjust_salary(Employee e) {
  foreach(e, employee_adjust_salary_node);
}

int main(void) {
  Employee e = NULL;

  with_open_file("work.txt", "r", employee_read, (Employee)&e);
  employee_print(e);

  employee_adjust_salary(e);
  employee_print(e);
  with_open_file("work.txt", "w", employee_print, e);

  employee_free(e);

  return EXIT_SUCCESS;
}