www.pudn.com > CRGAB.zip > VMKD.C

/* 
HEADER:         ; 
TITLE:          BASIC mkd() in C 
VERSION:        1.0; 
 
DESCRIPTION:    performs BASIC mkd() packing a value into a string 8 chars 
                long 
 
KEYWORDS:       ; 
SYSTEM:         Xenix 3.4b, MSDOS; 
FILENAME:       vmkd.c 
WARNINGS:       compile with -dNO_PROTOTYPE if your system does not 
                support prototyping, with -dFOR_MSDOS if you are compiling 
                for MSDOS with an ANSI standard compiler. 
                Defaults assume compiling with prototypes for 
                Xenix 3.4b on Altos 2086 computer. 
 
SEE-ALSO:       ; 
AUTHORS:        Vern Martin, 449 W. Harrison, Alliance, Ohio 44601; 
COMPILERS:      ECOSOFT ECO-C88, XENIX 3.4B STANDARD COMPILER; 
*/ 
 
#include "vernmath.h" 
 
#define WIDTH 8 
 
char *vmkd(amt) 
double amt; 
{ 
/* local int */ 
    int e;      /* exponent */ 
    double mantissa = frexp(amt,&e); 
 
    int i,sign = 1; 
 
    static unsigned char c[WIDTH]; 
    static double k[ WIDTH -1 ] = { 
        2.7755575615628914e-17, 
        7.1054273576010019e-15, 
        1.8189894035458565e-12, 
        4.6566128730773926e-10, 
        1.1920928955078125e-07, 
        3.0517578125000000e-05, 
        7.8125000000000000e-03, 
    }; 
 
/* make mantissa a positive number if necessary */ 
    if (mantissa < 0.0) { 
        sign = -1; 
        mantissa *= (double) sign; 
    } 
 
/* adjust result by multiplying mantissa by 2 until mantissa is greater than 1, 
    each time you multiply the mantissa by 2, subtract 1 from 
    the power you raise two by, in this way we duplicate the values 
    returned by BASIC's mkd() which returns 1.x * 2^e, where as 
    frexp() returns .x * 2^e */ 
 
    while(mantissa < 1.0) { 
        mantissa *= 2.0; 
        e--; 
    } 
 
    c[ WIDTH - 1 ] = (unsigned char) (e + 129); 
 
/* total first 3 chars multiplied by there respective factors */ 
    for ( i = WIDTH - 2; i >= 0;i-- ) { 
        if (mantissa < k[ i ]) c[ i ] = (unsigned char) 0; 
        else { 
            c[ i ] = (unsigned char) (mantissa/k[ i ]); 
            mantissa -= c[ i ] * k[ i ]; 
        } 
    } 
 
/* unless the number is negative, reverse next to last char */ 
    if (sign != -1) { 
        c[ WIDTH - 2 ] -= (unsigned char) 128; 
    } 
 
    if (amt == 0.0) c[ WIDTH - 1 ] = (unsigned char) 0; 
 
 
    return((char *)c); 
}