Thread: INFINITY problem

I am implementing a fibonacci heap and i require a negative infinity to delete a node and i used the INFINITY directive but the code is not compiling i assume its not defined in <stdio.h> or <stdlib.h> so i wish to know the header that supports this thing so i can get going..

ok i am using CodeBlocks Gnu C Compiler i think the 2008 version..

Then it is probably in the math.h header file. Also gcc uses versions like 3.4.5.

Jim

The macro INFINITY is defined in <math.h> for C99 and C11.
In C89 there is no Standard way to use infinity. You may try, for example

Code:

const double negativeinf = -3.14/0;

ok i'll definitely try that thanks guys

With GCC you can also use the GCC built-ins:

Code:

static const double  negative_infinityd = -__builtin_inf();
static const float   negative_infinityf = -__builtin_inff();

This will also generate a warning if the current architecture or compiler options do not support 'infinity'.

If you need a fallback, you can use -HUGE_VAL (for doubles) or -HUGE_VALF (for floats) defined in math.h for the smallest possible finite negative value instead. If using GCC, you can also fetch them using the built-ins

Code:

#ifndef HUGE_VAL
#define HUGE_VAL __builtin_huge_val()
#endif
#ifndef HUGE_VALF
#define HUGE_VALF __builtin_huge_valf()
#endif

For portable code (and when writing highly optimized timing-sensitive code, telling the compiler to relax the IEEE floating-point rules), you can use -HUGE_VAL and HUGE_VAL as sentinels, as long as you make sure all data is within the range (-HUGE_VAL < data && data < HUGE_VAL), when reading or generating the values. That way you also know all your data is finite.