我的 C 语法有问题吗？

Question

Just before I start, I'd like to say that I'm new here, and I'm also 3 weeks into C programming, so I'm not as experienced.

This is a code to determine the day of the week using the doomsday method. Please note that the header and the main function is the template and is as it should be. Everything else underneath the main function and the corresponding declarations at the top is my code.

    /*
*  doomsday.c
*  A program to test a function dayOfWeek which determines which
*  day of the week a particular date falls on.
*  (only for dates after the start of the Gregorian calendar).
*
*  Program stub created by Richard Buckland on 17/03/14
*  This program by YOUR-NAME-HERE
*  Freely licensed under Creative Commons CC-BY-3.0
*
*
*/

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

#define THURSDAY 0
#define FRIDAY   1
#define SATURDAY 2
#define SUNDAY   3
#define MONDAY   4
#define TUESDAY  5
#define WEDNESDAY 6

#define TRUE 1
#define FALSE 0
#define DAYS_PER_WEEK 7

int dayOfWeek (int doomsday, int leapYear, int month, int day);
int doomsDate (int month, int leapYear, int doomsday);
int numDaysLeft (int numDays, int doomsdayDate, int day);
int doomsdayDate;
int numDays;

int main (int argc, char *argv[]) {

   assert (dayOfWeek (THURSDAY,  FALSE,  4,  4) == THURSDAY);
   assert (dayOfWeek (FRIDAY,    FALSE,  6,  6) == FRIDAY);
   assert (dayOfWeek (MONDAY,    FALSE,  8,  8) == MONDAY);
   assert (dayOfWeek (WEDNESDAY, FALSE, 10, 10) == WEDNESDAY);
   assert (dayOfWeek (FRIDAY,    FALSE, 12, 12) == FRIDAY);
   assert (dayOfWeek (THURSDAY,  FALSE,  9,  5) == THURSDAY);
   assert (dayOfWeek (FRIDAY,    FALSE,  5,  9) == FRIDAY);
   assert (dayOfWeek (SUNDAY,    FALSE,  7, 11) == SUNDAY);
   assert (dayOfWeek (TUESDAY,   FALSE, 11,  7) == TUESDAY);
   assert (dayOfWeek (WEDNESDAY, FALSE,  3,  7) == WEDNESDAY);

   assert (dayOfWeek (THURSDAY,  FALSE,  4,  5) == FRIDAY);
   assert (dayOfWeek (SATURDAY,  FALSE,  6,  5) == FRIDAY);
   assert (dayOfWeek (MONDAY,    FALSE,  8,  9) == TUESDAY);
   assert (dayOfWeek (WEDNESDAY, FALSE, 10,  9) == TUESDAY);
   assert (dayOfWeek (FRIDAY,    FALSE, 12, 20) == SATURDAY);
   assert (dayOfWeek (THURSDAY,  FALSE,  9,  9) == MONDAY);
   assert (dayOfWeek (FRIDAY,    FALSE,  5,  5) == MONDAY);
   assert (dayOfWeek (SUNDAY,    FALSE,  7,  7) == WEDNESDAY);
   assert (dayOfWeek (TUESDAY,   FALSE, 11, 11) == SATURDAY);
   assert (dayOfWeek (THURSDAY,  FALSE,  3, 30) == SATURDAY);

   assert (dayOfWeek (TUESDAY,   FALSE,  2,  28) == TUESDAY);
   assert (dayOfWeek (TUESDAY,   FALSE,  2,  27) == MONDAY);
   assert (dayOfWeek (THURSDAY,  FALSE,  1,  3)  == THURSDAY);

   printf ("all tests passed - You are awesome!\n");
   return EXIT_SUCCESS;
}

// given the doomsday for a year, and whether or not it is a
// leap year, this function return the day of the week for any
// given month and day in the year.

int dayOfWeek (int doomsday, int leapYear, int month, int day) {
   int dayOfWeek;

   // Call function
   doomsDate (month, leapYear, doomsdayDate);

   // Making numDays always positive
   if (day < doomsdayDate) {
       doomsdayDate = -(doomsdayDate);
       day = -(day);     
    }

    // Calculate how many days between given day and closest doomsday
    numDays = (day - doomsdayDate);

    // Conditions needed to be satisfied
    if ((numDays = 0)) {
       numDays = 0;         
    } else if (numDays >= DAYS_PER_WEEK) {
       numDays = numDays % DAYS_PER_WEEK;    
    } else if (numDays > 0 && numDays < DAYS_PER_WEEK) {
       numDays = numDays;    
    }

   // Final calculation for the day of the week
   dayOfWeek = (numDays + doomsday);

   return (dayOfWeek);
}

//Function to calculate nearest doomsday date
int doomsDate (int month, int leapYear, int doomsdayDate) {

   if (month == 1) {
      if (leapYear == TRUE){
         doomsdayDate = 11;          
      } else if (leapYear == FALSE){
         doomsdayDate = 10;    
      }
   } else if (month == 2) {
      if (leapYear == TRUE) {
         doomsdayDate = 29;          
      } else if (leapYear == FALSE) {  
         doomsdayDate = 28;
      } 
   } else if (month == 3){
      doomsdayDate = 0;    
   } else if (month == 4) {
      doomsdayDate = 4;    
   } else if (month == 6) {
      doomsdayDate = 6;    
   } else if (month == 8) {
      doomsdayDate = 8;    
   } else if (month == 10) {
      doomsdayDate = 10;    
   } else if (month == 12) {
      doomsdayDate = 12;    
   } else if (month == 7) {
      doomsdayDate = 11;    
   } else if (month == 11) {
      doomsdayDate = 7;    
   } else if (month == 9) {
      doomsdayDate = 5;    
   } else if (month == 5) {
      doomsdayDate = 9;
   }

return doomsdayDate;    
}

There's a mysterious error in my code which I cannot pin-point, but I believe it may lie within the variables that I have written or with the if-statements. All calculations seem to be correct, however, the code fails whenever the doomsday variable (in main function) is not equal to the corresponding answer. I've played around with my variables and it seems to me that their values aren't being changed as they should. Any tips?

EDIT: Updated code. Still fails at section 2 of asserts in main function. gcc accepts the code, debuggers return nothing.

Answer 1

At least this section will cause trouble;

if (month == 1) {
  if (leapYear = TRUE){
     doomsdayDate = 11;          
  } else if (leapYear = FALSE){
     doomsdayDate = 10;    
  }
} else if (month == 2) {
  if (leapYear = TRUE) {
     doomsdayDate = 29;          
  } else if (leapYear = FALSE) {  
     doomsdayDate = 28;
  } 
...

Several comparisons are actually assignments, for example;

if (leapYear = TRUE) {

should be

if (leapYear == TRUE) {

EDIT: You also seem to have some logic problems, in your method dayOfWeek you're using the global variable doomsdayDate without ever setting it. I assume you're missing a call to doomsDate somewhere. Also, had the variable been local, the compiler would have told you it was never initialised.

Answer 2

if ((numDays = 0))

should be:

if ((numDays == 0))

as it is requesting a condition, not setting the variable to 0.