ceil.c File Reference

Ceiling function. More...

#include "prim.h"

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Functions
double	ceil (double x)
	Ceiling function. More...

Variables
static const double	huge = 1.0e300

Detailed Description

Ceiling function.

Definition in file ceil.c.

Function Documentation

ceil()

double ceil

(

double

x

)

Ceiling function.

Parameters

x

Returns

x rounded toward -inf to integral value

Method
    Bit twiddling

Exception
    Inexact flag raised if x not equal to ceil(x).

Definition at line 63 of file ceil.c.

References huge.

Referenced by cceil(), RealNumber::Ceiling(), Dragon4(), round(), and trunc().

{
    int32_t i0,i1,j0;
    uint32_t i,j;
    EXTRACT_WORDS(i0,i1,x);
    j0 = ((i0>>20)&0x7ff)-0x3ff;
    if(j0<20) {
        if(j0<0) {          /* raise inexact if x != 0 */
            if(huge+x>0.0) {        /* return 0*sign(x) if |x|<1 */
                if(i0<0) {
                    i0=0x80000000;
                    i1=0;
                }
                else if((i0|i1)!=0) {
                    i0=0x3ff00000;
                    i1=0;
                }
            }
        } else {
            i = (0x000fffff)>>j0;
            if(((i0&i)|i1)==0) return x; /* x is integral */
            if(huge+x>0.0) {        /* raise inexact flag */
                if(i0>0) i0 += (0x00100000)>>j0;
                i0 &= (~i);
                i1=0;
            }
        }
    } else if (j0>51) {
        if(j0==0x400) return x+x;   /* inf or NaN */
        else return x;          /* x is integral */
    } else {
        i = ((uint32_t)(0xffffffff))>>(j0-20);
        if((i1&i)==0) return x;     /* x is integral */
        if(huge+x>0.0) {        /* raise inexact flag */
            if(i0>0) {
                if(j0==20) i0+=1;
                else {
                    j = i1 + (1<<(52-j0));
                    // NOTICE: Is this a correct cast?
                    if((int32_t)j<(int32_t)i1) i0+=1;   /* got a carry */
                    i1 = j;
                }
            }
            i1 &= (~i);
        }
    }
    INSERT_WORDS(x,i0,i1);
    return x;
}

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Variable Documentation

huge

const double huge = 1.0e300

static

Definition at line 48 of file ceil.c.

Referenced by ceil().