代碼如下：

#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; }

work.txt

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

轉載于:https://www.cnblogs.com/code-style/p/3286984.html

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