Thread: C Ranges

Originally Posted by Adak

The C language has some quirks in it's order of operations.

It may, but there not for that example.


Quzah.

Code:

if(JULIAN>335 && <=365)

Read that outloud. If Julian is greater than 335 AND ______ is less than or equal to 365 ...

You also don't even have to have half of those checks in.

Code:

if( x < 0 )
    error, do something...
else
if( x < 10 )
    between 0 and 9
else
if( x < 20 )
    between 10 and 19
...

But it's up to you.


Quzah.

> If there is another way to make this operation work please take the time to explain it,
Do you know about structures yet?

> Instead of using 12 if statements in a row, why not make it one switch statement?
Because standard C doesn't have ranges on cases.
365 lines of switch/case is hardly clear code.

Oh, and the cascasded indent on your if - not pretty.

Code:

/* ***************************
*C Program Code::Blocks v1.0         *
*Written by: EvoTone                       *
*Date: Sept., 2006                           *
**************************** */
#include <stdio.h>

typedef struct /*This structs DATE_RANGE w/ 3 constants num/num/char*/
{
    const int lower; /*Defines a number as lower*/
    const int upper; /*Defines a number as "upper"*/
    const char * month; /*Defines month names*/
} DATE_RANGE; /*Name of the struct*/

static const DATE_RANGE date_range[]/*Defines struct as array,date_range[]*/
{
    {   0,  31, "January"   },   /*Defines lower/upper/month variables in struct*/
    {  31,  59, "February"  }, /*"           "*/
    {  59,  91, "March"     },   /*"           "*/ 
    {  91, 121, "April"     },     /*"           "*/ 
    { 121, 152, "May"       },   /*"           "*/ 
    { 152, 182, "June"      },    /*"           "*/ 
    { 182, 213, "July"      },      /*"           "*/ 
    { 213, 244, "August"    },    /*"           "*/ 
    { 244, 274, "September" },  /*"           "*/ 
    { 274, 305, "October"   },     /*"           "*/ 
    { 305, 335, "November"  },   /*"           "*/ 
    { 335, 365, "December"  }     /*"           "*/ 
};

int main(void)
{
    int i;
    int julian; /*input value from user, needing conversion.*/

    /*Intro. & Instructions*/
    printf("This is a Julian to Calendar Date conversion program\n");
    printf("you may input any Julian date and the corresponding\n");
    printf("Calendar Date will be calculated for you\n\n");

                             /*Input Section*/
    printf("Please enter the Julian date: (whole number format)\n");
    scanf("%i", &julian);
    printf("Well silly we know it's Year: 2006!\n\n");


                            /*Calculation Section*/
    for (i = 0; i < (sizeof(date_range) / sizeof(date_range[0])); i++) /*Loop*/
    {
        if ((julian > date_range[i].lower) && (julian <= date_range[i].upper))
        {
            printf("And we know it's: %s\n", date_range[i].month);
            break;
        }
    }

    if( i == ( sizeof(date_range) / sizeof(date_range[0]) ) )
        printf("Don't mess with me stupid!!...Julian Dates are only 1-365!\n");

    return (0);

}

I think I'm getting what this is supposed to do but, there is syntax errors at line 15 and 48 that I can't figure out. I hadn't previously fooled with "struct" or setting an "array" in this manner so, even after reading up on it, I can't fix it. Little help please. I have added notes to places, telling the thought process I am taking in my attempt to explaining this.

~EvoTone~

Have you been programming in Java?

Code:

static const DATE_RANGE date_range[]
{

->

Code:

static const DATE_RANGE date_range[] =
{

That's pretty much how I'd do it, too, except as Quzah said, if you order the dates correctly, you only have to store their upper bounds.

For some reason in the cut'n'paste operation the "=" went missing. I did actually compile, run and test the code (honest).

Of course you aren't dealing with leap years, so your program will only work approximately 3/4 of the time. This year's OK, next year's OK, then in 2008 it will break.

Completely untested, but even that complete code has redundancy in it. Take a look at this:

Code:

/* ***************************
*C Program Code::Blocks v1.0         *
*Written by: EvoTone                       *
*Date: Sept., 2006                           *
**************************** */
#include <stdio.h>

typedef struct /*This structs DATE_RANGE w/ 2 constants num, char */
{
    const int lower; /*Defines a number as lower*/
    const char * month; /*Defines month names*/
} DATE_RANGE; /*Name of the struct*/

static const DATE_RANGE date_range[]/*Defines struct as array,date_range[]*/
{
    {   0,  "January"   },   /*Defines lower/upper/month variables in struct*/
    {  31,  "February"  }, /*"           "*/
    {  59,  "March"     },   /*"           "*/ 
    {  91, "April"     },     /*"           "*/ 
    { 121, "May"       },   /*"           "*/ 
    { 152, "June"      },    /*"           "*/ 
    { 182, "July"      },      /*"           "*/ 
    { 213, "August"    },    /*"           "*/ 
    { 244, "September" },  /*"           "*/ 
    { 274, "October"   },     /*"           "*/ 
    { 305, "November"  },   /*"           "*/ 
    { 335, "December"  }     /*"           "*/ 
};

int main(void)
{
    int i;
    int julian; /*input value from user, needing conversion.*/

    /*Intro. & Instructions*/
    printf("This is a Julian to Calendar Date conversion program\n");
    printf("you may input any Julian date and the corresponding\n");
    printf("Calendar Date will be calculated for you\n\n");

                             /*Input Section*/
    printf("Please enter the Julian date: (whole number format)\n");
    scanf("%i", &julian);
    printf("Well silly we know it's Year: 2006!\n\n");


                            /*Calculation Section*/
    for (i = 0; i < (sizeof(date_range) / sizeof(date_range[0])); i++) /*Loop*/
    {
        if (julian > date_range[i].lower)
        {
            printf("And we know it's: %s\n", date_range[i].month);
            break;
        }
    }

    if (i  > 365 )
        printf("Don't mess with me stupid!!...Julian Dates are only 1-365!\n");

    return (0);

}

You only need to test for either the upper or the lower bound, and as the loop breaks out afterwards it will not continue.

As has been pointed out, modifications to the hardcoded values are required to cater for leap years (bearing in mind that altough 2000 was fortunately a leap year, 2100 will not be).