Question

10.3 Name_year in C - phase 3

This lab is part 2 of a series of 3 labs that will walk you through the process of creating a C struct and related functions that are the equivalent of the Name_year class you created in chapter 9.

For this phase, we will

• Create an init_name_year() function that initializes a Name_year object.
• Move the object initialization logic from create_name_year() to init_name_year().
• Create a function called compare_name_year() to compare two Name_year objects.

The function declarations are:

int init_name_year(Name_year * ny, const char * name, int year);
int compare_name_year(const Name_year * ny1, const Name_year * ny2);

init_name_year() should contain all the code originally in create_name_year() that actually initializes the data. That is, it should

• use malloc() to allocate memory for a copy of the name
• use strcpy() to copy the name
• store the year in the struct\

Name_year should return 1 if everything worked (that is, if we were able to allocate memory for the name), and 0 to indicate failure.

compare_name_year() will return a value consistent with the convention elsewhere in the C library (specifically strcmp()). The return value is

• -1 if ny1 < ny2
• 0 if ny1 == ny2
• 1 if ny1 > ny2

One Name_year is considered to be greater than another if the name in one is "greater than" the name in the other, as determined by the strcmp() function. If the names are the same, then the comparison is based on the year. Here is the pseudocode for compare_name_year():

compare the names using `strcmp()`, and store the return value
if strcmp() returned a non-zero value
    return that value
else
    compare the years and return
        

-1 if ny1->year < ny2->year

1 if ny1->year > ny2->year

0 if they are equal

I will review your final code to ensure that the following things are done correctly. You will lose points on the assignment for each one that is not correct:

• Your code should be reasonably and consistently indented.
• Your header file must be able to be included twice.
• All functions must be defined in the source file (Name_year.c).
• The verify_year() function should be defined in the .c file but not declared in the .h file.
• create_name_year() should call init_name_year() to initialize the name and year fields in the struct

-----------------------

name_year_test.c is given:

#include "Name_year.h"

#define _CRT_SECURE_NO_WARNINGS

#include
#include
#include

void print_name_year(const Name_year * ny)
{
   printf("%s,%d\n", ny->name, ny->year);
}

int qsort_compare(const void * lhs, const void * rhs)
{
   Name_year * lny = (Name_year *)lhs;
   Name_year * rny = (Name_year *)rhs;
   return compare_name_year(lny, rny);
}

int main()
{
   char * ny_format = "%s,%d\n";

#if PHASE >= 1

   puts("Phase 1 tests");

   // Make sure we can create an object and get the data back.
   // We're creating the name as a local array so that we can
   // make sure that create_name_year() does not merely make
   // a copy of the pointer.
   char stroustrup[20];
   strcpy(stroustrup, "Stroustrup");
   Name_year * ny_stroustrup = create_name_year(stroustrup, 1950);
   stroustrup[0] = '\0';
   print_name_year(ny_stroustrup);

   // Make sure we can create a second object independent from the first one.
   char knuth[20];
   strcpy(knuth, "Knuth");
   Name_year * ny_knuth = create_name_year(knuth, 1938);
   knuth[0] = '\0';
   print_name_year(ny_stroustrup);
   print_name_year(ny_knuth);

   destroy_name_year(ny_stroustrup);
   destroy_name_year(ny_knuth);

#endif

#if PHASE >= 2

   puts("Phase 2 tests");

   // Make sure we can change the year.
   Name_year * ny_dijkstra = create_name_year("Dijkstra", 1980);
   print_name_year(ny_dijkstra);
   set_year(ny_dijkstra, 1930);
   print_name_year(ny_dijkstra);
   destroy_name_year(ny_dijkstra);

   {
       // Make sure the proper status is returned by create_name_year().
       Name_year * ny_lovelace = create_name_year("Lovelace", 1815);
       if (ny_lovelace != NULL)
           puts("Error: invalid status returned for invalid year in create_name_year");
       else
           puts("correct status returned for invalid year in create_name_year");
   }

   // Make sure the proper exception is thrown from set_year().
   Name_year * ny_lovelace = create_name_year("Lovelace", 1915);
   if (set_year(ny_lovelace, 1815))
       puts("Error: invalid status returned for invalid year in set_year");
   else
       puts("Correct status returned for invalid year in set_year");

   // Make sure trying to set an invalid year did not change the object.
   print_name_year(ny_lovelace);
   destroy_name_year(ny_lovelace);

#endif

#if PHASE>=3

   puts("Phase 3 tests");

   // Create a vector of Name_pairs.
   Name_year nys[6];
   init_name_year(&nys[0], "Stroustrup", 1950);
   init_name_year(&nys[1], "Knuth", 1938);
   init_name_year(&nys[2], "Smith", 1961);
   init_name_year(&nys[3], "Smith", 1960);
   init_name_year(&nys[4], "Dijkstra", 1930);
   init_name_year(&nys[5], "Knuth", 1938);

   int num_nys = sizeof(nys) / sizeof(nys[0]);

   // Make sure we can print them out
   puts("");
   puts("Before sorting");
   for (int i = 0; i < num_nys; i++)
       print_name_year(&nys[i]);

   // Make sure the two Knuths are equal.
   int cmp = compare_name_year(&nys[1], &nys[5]);
   if (cmp != 0)
       printf("Error comparing equal items: returned %d for equal objects\n", cmp);

   cmp = compare_name_year(&nys[4], &nys[0]);
   if (cmp != -1)
       printf("Error comparing unequal items: returned %d for object 1 < object2\n", cmp);

   cmp = compare_name_year(&nys[2], &nys[1]);
   if (cmp != 1)
       printf("Error comparing unequal items: returned %d for object 1 > object2\n", cmp);

   cmp = compare_name_year(&nys[3], &nys[2]);
   if (cmp != -1)
       printf("Error comparing unequal items (equal names): returned %d for object 1 < object2\n", cmp);

   // Make sure we can sort. We'll use stable_sort to make sure
   // the year is taken into account (the Smiths should swap relative
   // position).
   qsort(nys, num_nys, sizeof(Name_year), qsort_compare);
   puts("");
   puts("After sorting");
   for (int i = 0; i < num_nys; i++)
       print_name_year(&nys[i]);

#endif

   return 0;
}

-----------------

find name_year.h and name_year.c as stated in the question

Answer 1

#ifndef NAME_YEAR_H
#define NAME_YEAR_H
typedef struct {
        char * name;
        int year;
}Name_year;

Name_year * create_name_year(const char * name, int year);
void destroy_name_year(Name_year * ny);
int set_year(Name_year* ny, int y);
int init_name_year(Name_year * ny, const char * name, int year);
int compare_name_year(const Name_year * ny1, const Name_year * ny2);


#endif // NAME_YEAR_H

----------------------------------------------Name_year.c-----------------------------

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "Name_year.h"

int verify_year(int y) {
        return (y >= 1900);
}

Name_year* create_name_year(const char *name, int year) {
        if(!verify_year(year)) {
                return NULL;
        }

        Name_year *ny = (Name_year*) malloc(sizeof(Name_year));
        if(ny == NULL) {
                return NULL;
        }

        if(init_name_year(ny, name, year)) {
                return ny;
        }
        
        return NULL;
}

void destroy_name_year(Name_year * ny)
{
        free(ny); // delete allocated memory of ny
        ny = NULL; // assign NULL to ny
}

int set_year(Name_year* ny, int y) {
        if(verify_year(y)) {
                ny->year = y;
                return 1;
        }
        return 0;
}

int init_name_year(Name_year * ny, const char * name, int year) {               
        ny->name = (char*) malloc(sizeof(char) * (strlen(name) + 1));
        if(ny->name == NULL) {
                return 0;
        }
        strcpy(ny->name, name);
        ny->year = year;
        return 1;
}


int compare_name_year(const Name_year * ny1, const Name_year * ny2) {
        if(ny1->year < ny2->year) {
                return -1;
        } else if(ny1->year > ny2->year) {
                return 1;
        } else {
                return 0;
        }

}

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