函数式C代码

代码如下：

#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