abs, labs, llabs, _abs64

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06/05/2017

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The latest version of this topic can be found at abs, labs, llabs, _abs64.

Calculates the absolute value of the argument.

Syntax

int abs(   
   int n   
);  
long abs(   
   long n   
);   // C++ only  
long long abs(   
   long long n   
);   // C++ only  
double abs(   
   double n   
);   // C++ only  
long double abs(  
   long double n  
);   // C++ only  
float abs(  
   float n   
);   // C++ only  
long labs(  
   long n   
);  
long long llabs(  
   long long n   
);  
__int64 _abs64(   
   __int64 n   
);

Parameters

n
Numeric value.

Return Value

The abs, labs, llabs and _abs64 functions return the absolute value of the parameter n. There is no error return.

Remarks

Because C++ allows overloading, you can call overloads of abs that take and return long, long long, float, double, and long double values. These overloads are defined in the <cmath> header. In a C program, abs always takes and returns an int.

Microsoft Specific

Because the range of negative integers that can be represented by using any integral type is larger than the range of positive integers that can be represented by using that type, it's possible to supply an argument to these functions that can’t be converted. If the absolute value of the argument cannot be represented by the return type, the abs functions return the argument value unchanged. Specifically, abs(INT_MIN) returns INT_MIN, labs(LONG_MIN) returns LONG_MIN, llabs(LLONG_MIN) returns LLONG_MIN, and _abs64(_I64_MIN) returns _I64_MIN. This means that the abs functions cannot be used to guarantee a positive value.

End Microsoft Specific

Requirements

Routine	Required C header	Required C++ header
`abs`, `labs`, `llabs`	<math.h> or <stdlib.h>	<cmath>, <cstdlib>, <stdlib.h> or <math.h>
`_abs64`	<stdlib.h>	<cstdlib> or <stdlib.h>

To use the overloaded versions of abs in C++, you must include the <cmath> header.

Example

This program computes and displays the absolute values of several numbers.

// crt_abs.c  
// Build: cl /W3 /TC crt_abs.c  
// This program demonstrates the use of the abs function  
// by computing and displaying the absolute values of  
// several numbers.  
  
#include <stdio.h>  
#include <math.h>  
#include <stdlib.h>  
#include <limits.h>  
  
int main( void )  
{  
    int ix = -4;  
    long lx = -41567L;  
    long long llx = -9876543210LL;  
    __int64 wx = -1;  
  
    // absolute 32 bit integer value  
    printf_s("The absolute value of %d is %d\n", ix, abs(ix));  
  
    // absolute long integer value  
    printf_s("The absolute value of %ld is %ld\n", lx, labs(lx));  
  
    // absolute long long integer value  
    printf_s("The absolute value of %lld is %lld\n", llx, llabs(llx));  
  
    // absolute 64 bit integer value  
    printf_s("The absolute value of 0x%.16I64x is 0x%.16I64x\n", wx,   
        _abs64(wx));  
  
    // Integer error cases:  
    printf_s("Microsoft implementation-specific results:\n");  
    printf_s(" abs(INT_MIN) returns %d\n", abs(INT_MIN));  
    printf_s(" labs(LONG_MIN) returns %ld\n", labs(LONG_MIN));  
    printf_s(" llabs(LLONG_MIN) returns %lld\n", llabs(LLONG_MIN));  
    printf_s(" _abs64(_I64_MIN) returns 0x%.16I64x\n", _abs64(_I64_MIN));  
}

The absolute value of -4 is 4  
The absolute value of -41567 is 41567  
The absolute value of -9876543210 is 9876543210  
The absolute value of 0xffffffffffffffff is 0x0000000000000001  
Microsoft implementation-specific results:  
 abs(INT_MIN) returns -2147483648  
 labs(LONG_MIN) returns -2147483648  
 llabs(LLONG_MIN) returns -9223372036854775808  
 _abs64(_I64_MIN) returns 0x8000000000000000

.NET Framework Equivalent

System::Math::Abs

共用方式為