pointer to structure

Question

1.00/5 (2 votes)

See more:

i wrote the following program to separate the real and fractional parts of a number, where i declared a pointer to a structure. The program compiles perfectly, but does not execute.
I compiled using the Visual Studio command prompt. The part that causes trouble is where I have declared a pointer to the structure.

C#

#include<stdio.h>
#include<stdlib.h>
#define MAX 12
struct REAL
{
    int left;
    int right;
} *rl;

int main()
{
    //rl = (struct REAL *)malloc(sizeof(struct REAL));
    int l=0, r=0;
    int number[MAX];
    int ch, count = 0, sign=1;
    while((ch = getchar()) != '.')
    {
        if(ch == '-')
            sign = -1;
        else
            l = l*10 + (ch - '0');
    }
    rl->left = sign*l;
    printf("left = %d\n", rl->left);
    while((ch = getchar()) != '\n')
    {
        r = r*10 + (ch - '0');
    }
    rl->right = r;
    printf("right = %d\n", rl->right);
    return 0;
}

Please point out the error!
thanx in advance.

(P.S. I am aware of the implementation of a real number in C, using the sign, exponent and fraction form(32 = 1+8+23).
I am learning some new data structure concepts. This program was a solution for a question in the book by Aaron M. Tenenbaum.)

Posted 7-May-12 7:18am

kr_harsha

Updated 7-May-12 16:24pm

v3

Add a Solution

Comments

Sergey Alexandrovich Kryukov 7-May-12 13:27pm

Reason for my vote of 1
Should I also mark it off-topic? Here is why: this is a site for software developers and students; and software developers never say "it does not work", only lame users do. The software developers, even the beginners, say what exactly goes wrong, in what line of code. They provide comprehensive issue report.

In your case, you could run it under debugger to see what's wrong and ask a question if you still cannot understand the behavior or don't see how to fix it.

Use "Improve question" above.

--SA

wizardzz 7-May-12 13:28pm

Reason for my vote of 1
What is the actual problem you are having?

Sergey Alexandrovich Kryukov 7-May-12 13:28pm

By the way, why separate fractional and integer parts of a number, ever?
--SA

2 solutions

Solution 2

Among other things: you cannot really make a satisfactory model of a real number using two integers. The best known model is the floating-point model which is based on significand, coefficient, mantissa, and exponent and already exists and standardized as IEEE 754:
http://en.wikipedia.org/wiki/Floating_point[^],
http://en.wikipedia.org/wiki/IEEE_754[^].

This is a binary representation; and you are trying to work with strings instead of binary objects, which is itself is a pointless activity — working with string representation of data instead of data itself.

By the way, do you understand that a mathematical real number, its single instance, in general case, carries infinite amount of information?

I would advice you to stop doing what you are doing and learn some mathematics and elementary computer science around these problems.

—SA

Posted 7-May-12 7:40am

Sergey Alexandrovich Kryukov

Comments

JackDingler 7-May-12 14:06pm

If your number range is finite, fixed decimal binary works well.. Haven't needed it since 486s went out of style... Floating point is too fast now, to make optimizations like that worthwhile.

Sergey Alexandrovich Kryukov 7-May-12 19:43pm

Sure.
--SA

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Accepted Answer · 2012-05-07T07:33:00

Solution 1

kr_harsha wrote:
Please point out the error!

Oh the irony: the error is the pointer!
You didn't allocate a struct for it.

A quick & dirty fix (the code is far from being perfect): add the following lines immediately before the first while loop:

C

struct REAL real;
rl = ℜ

and the statement r=0; immediately before the second while loop.

Posted 7-May-12 7:33am

CPallini

Comments

Sergey Alexandrovich Kryukov 7-May-12 19:43pm

Sure, a 5.
--SA