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.

OK, I just didn't know if I could describe it well enough, otherwise.

Do take note of quzah's tip on the if statements. You're leaving out the second "JULIAN", inside the parenthesis.

if ((hour > 2) && (hour < 4)) printf("\n Time to get that report out to division");

hour needs to be included before the && as well as after it. Each part of the compound expression is evaluated separately, and then later, evaluated as a whole. That's what the extra parenthesis ensure.

Originally Posted by EvoTone

Thanks for the tip on wrapping evaluations but, what I don't want is for you guys to write my
program for me. Cause then I have no idea what the code does in a step-by-step method. And I am none the wiser for it~~

Here is what I am learning on:

ALWAYS PUT YOUR CODE BETWEEN CODE TAGS!

Code:

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

{

    int JULIAN; /*input value from user, needing converted.*/

    /*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");


                            /*Calcualtion Section*/
if((JULIAN >0) && (<=31))  printf("And we also know it's: January\n");

    if(JULIAN >31 && <=59 )  printf("And we also know it's: Febuary\n");[/COLOR]

        if(JULIAN>59 && <=91)  printf("And we also know it's: March\n");

            if(JULIAN>91 && <=121)  printf("And we also know it's: April\n");

                if(JULIAN>121 && <=152)  printf("And we also know it's: May\n");

                   if(JULIAN>152 && <=182)  printf("And we also know it's: June\n");

                        if(JULIAN>182 && <=213)  printf("And we also know it's: July\n");

                            if(JULIAN>213 && <=244)   printf("And we also know it's: August\n");

                               if(JULIAN>244 && <=274)  printf("And we also know it's: September\n");

                                   if(JULIAN>274 && <=305)  printf("And we also know it's: October\n");

                                     if(JULIAN>305 && <=335)  printf("And we also know it's: November\n");

                                       if(JULIAN>335 && <=365)  printf("And we also know it's: December\n");
                                       else
                 if(JULIAN>365)  printf("Don't mess with me stupid!!...Julian Dates are only 1-365!\n");

    return (0);

}

So here is my exact source code copied and pasted from my IDE, code::blocks v.1.0(GNU GCC
Compiler). If there is another way to make this operation work please take the time to explain it, if it's way out in left field that is. And please don't comment on how to complete any other part of this program except this part........~please~

~EvoTone~

Any time you see a good deal of something in your code that's repeated several times, especially if it's repeated in the same function, you can be sure the design of the program should be improved.

Look how many times the phrase "And we can be sure that..." is included in your code. Try and make it so it's only included once!

Instead of using 12 if statements in a row, why not make it one switch statement? That's exactly the kind of thing that the switch statement was created for. The indentation you have for the if statements reflects a chain of interlinked if statements, like a cascade. In fact, they all are independent statements, and should all go to the left side, even with the first if statement.
(but all should be replaced by one switch statement)

In your prompt for "whole number format", it'd be helpful if you showed an example:
of just what a "whole number format" date, really is. (eg: give your example here). Since you're getting critical input from your user, you need to think about making sure that the user understands, and that you are actually checking, their input. (you'll do a lot more input checking on programs, later on)

Be considerate of your user - "silly" and "stupid" reflect an inconsiderate and juvenile light on your program. It's rarely good to put a little humor into a program, just because it gets old, and what's funny to one person, isn't to others. You'd be surprised how angry user's get when they're called names by a computer program!

Adak

> 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.

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.

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~

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).