Splitting a numbers binary representation for a double. Post: 302665447

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Homework and Emergencies Homework & Coursework Questions Splitting a numbers binary representation for a double. Post 302665447 by robin_simple on Monday 2nd of July 2012 09:38:27 PM

07-02-2012

Registered User

Code:

#include <iostream>
#include <stdlib.h>
using namespace std;

int main()
{
        char *hex_key = "abcdef012345678";
        long long key = strtoll( hex_key, NULL, 16 );

        cout << key << endl;
}

on compilation:
g++ b.cpp
b.cpp: In function ‘int main()’:
b.cpp:7: warning: deprecated conversion from string constant to ‘char*’

output:
./a.out
773738358679819896

Is there anything I can do to get rid of the warning?

Also, the full hex_key is 9abcdef012345678 which is different from what I used in the above code because of the 9 at the beginning. The output of this is 9223372036854775807
which is different from a result shown on a webpage that calculates hexadecimal numbers. All the outputs for the other hex_key values are consistent with the calculating website. Why is this number different?

Also, in your first reply you gave me

Code:

unsigned char *cval = "123";
    int val = 0;
    int i;

    for( i = 0; i < strlen( cval ); i++ )
    {
        val <<= 4;
        val += cval[i] - '0';
    }
    printf( "%x\n", val );

and I am wondering why you subtract '0' and why you shift 4. Is it necessary to shift << by four each time you add a new hex digit?

---------- Post updated at 08:38 PM ---------- Previous update was at 12:56 PM ----------

ok, strtoull() was the function that gets the whole 16 hex digits. the unsigned long long type was what I should have been using.

robin_simple

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LEARN ABOUT FREEBSD

atol

ATOL(3) 						   BSD Library Functions Manual 						   ATOL(3)

NAME

     atol, atoll -- convert ASCII string to long or long long integer

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <stdlib.h>

     long
     atol(const char *nptr);

     long long
     atoll(const char *nptr);

DESCRIPTION

     The atol() function converts the initial portion of the string pointed to by nptr to long integer representation.

     It is equivalent to:

	   strtol(nptr, (char **)NULL, 10);

     The atoll() function converts the initial portion of the string pointed to by nptr to long long integer representation.

     It is equivalent to:

	   strtoll(nptr, (char **)NULL, 10);

COMPATIBILITY

     The FreeBSD implementations of the atol() and atoll() functions are thin wrappers around strtol() and strtoll() respectively, so these func-
     tions will affect the value of errno in the same way that the strtol() and strtoll() functions are able to.  This behavior of atol() and
     atoll() is not required by ISO/IEC 9899:1990 (``ISO C90'') or ISO/IEC 9899:1999 (``ISO C99''), but it is allowed by all of ISO/IEC 9899:1990
     (``ISO C90''), ISO/IEC 9899:1999 (``ISO C99'') and IEEE Std 1003.1-2001 (``POSIX.1'').

ERRORS

     The functions atol() and atoll() may affect the value of errno on an error.

SEE ALSO

     atof(3), atoi(3), strtod(3), strtol(3), strtoul(3)

STANDARDS

     The atol() function conforms to ISO/IEC 9899:1990 (``ISO C90'').  The atoll() function conforms to ISO/IEC 9899:1999 (``ISO C99'').

BSD
								   May 14, 2013 							       BSD