projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| a62df508 | 1 | /* @(#)floor.c 4.2 9/11/85; 1.2 (ucb.elefunt) %G% */ |
| 2db37043 ZAL |
2 | |
| 3 | /* | |
| 4 | * floor and ceil-- greatest integer <= arg | |
| 5 | * (resp least >=) | |
| 6 | */ | |
| 7 | ||
| 8 | double modf(); | |
| 9 | ||
| 10 | double | |
| 11 | floor(d) | |
| 12 | double d; | |
| 13 | { | |
| 14 | double fract; | |
| 15 | ||
| 16 | if (d<0.0) { | |
| 17 | d = -d; | |
| 18 | fract = modf(d, &d); | |
| 19 | if (fract != 0.0) | |
| 20 | d += 1; | |
| 21 | d = -d; | |
| 22 | } else | |
| 23 | modf(d, &d); | |
| 24 | return(d); | |
| 25 | } | |
| 26 | ||
| 27 | double | |
| 28 | ceil(d) | |
| 29 | double d; | |
| 30 | { | |
| 31 | return(-floor(-d)); | |
| 32 | } | |
| 33 | ||
| 34 | /* | |
| 35 | * algorithm for rint(x) in pseudo-pascal form ... | |
| 36 | * | |
| 37 | * real rint(x): real x; | |
| 38 | * ... delivers integer nearest x in direction of prevailing rounding | |
| 39 | * ... mode | |
| 40 | * const L = (last consecutive integer)/2 | |
| 41 | * = 2**55; for VAX D | |
| 42 | * = 2**52; for IEEE 754 Double | |
| 43 | * real s,t; | |
| 44 | * begin | |
| 45 | * if x != x then return x; ... NaN | |
| 46 | * if |x| >= L then return x; ... already an integer | |
| 47 | * s := copysign(L,x); | |
| 48 | * t := x + s; ... = (x+s) rounded to integer | |
| 49 | * return t - s | |
| 50 | * end; | |
| 51 | * | |
| 52 | * Note: Inexact will be signaled if x is not an integer, as is | |
| 53 | * customary for IEEE 754. No other signal can be emitted. | |
| 54 | */ | |
| 55 | #ifdef VAX | |
| 56 | static long Lx[] = {0x5c00,0x0}; /* 2**55 */ | |
| 57 | #define L *(double *) Lx | |
| 58 | #else /* IEEE double */ | |
| 59 | static double L = 4503599627370496.0E0; /* 2**52 */ | |
| 60 | #endif | |
| 61 | double | |
| 62 | rint(x) | |
| 63 | double x; | |
| 64 | { | |
| 65 | double s,t,one = 1.0,copysign(); | |
| 66 | #ifndef VAX | |
| 67 | if (x != x) /* NaN */ | |
| 68 | return (x); | |
| 69 | #endif | |
| 70 | if (copysign(x,one) >= L) /* already an integer */ | |
| 71 | return (x); | |
| 72 | s = copysign(L,x); | |
| 73 | t = x + s; /* x+s rounded to integer */ | |
| 74 | return (t - s); | |
| 75 | } |