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/* ENG.C - Format floating point in engineering notation */
/* Released to public domain by author, David Harmon, Jan. 1994 */
#include <stdio.h>
char *eng(double value, int places)
{
const char * const prefixes[] = {
"a", "f", "p", "n", "", "m", "", "k", "M", "G", "T"
};
int p = 6;
static char result[30];
char *res = result;
if (value < 0.)
{
*res++ = '-';
value = -value;
}
while (value != 0 && value < 1. && p > 0)
{
value *= 1000.;
p--;
}
while (value != 0 && value > 1000. && p < 10 )
{
value /= 1000.;
p++;
}
if (value > 100.)
places--;
if (value > 10.)
places--;
sprintf(res, "%.*f %s", places-1, value, prefixes[p]);
return result;
}
#ifdef TEST
#include <stdio.h>
main()
{
double w;
for (w = 1e-19; w < 1e16; w *= 42)
printf(" %g W = %sW\n", w, eng(w, 3));
return 0;
}
#endif
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