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Digital-Research-Source-Code/CPM OPERATING SYSTEMS/CPM 68K/cpm68k_pgms/sdbas/MTH.C
Sepp J Morris 31738079c4 Upload 
Digital Research
2020-11-06 18:50:37 +01:00

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/* SDB - string arithmetic routines */
#include <ctype.h> /*dns*/
/* useful definitions */
#define TRUE 1
#define FALSE 0
#define NUMBERMAX 99
#define EOS 0
/* db_cmp - compare two signed numeric strings */
int db_cmp(arg1,arg2)
char *arg1,*arg2;
{
int sign1,sign2;
/* get the signs of the arguments */
sign1 = getsign(&arg1);
sign2 = getsign(&arg2);
/* compute the result */
if (sign1 == sign2) {
if (sign1 == 1)
return (compare(arg1,arg2));
else
return (compare(arg2,arg1));
}
/* signs are different */
return (sign1);
}
/* db_add - add two signed numeric strings */
db_add(result,arg1,arg2)
char *result,*arg1,*arg2;
{
int signr,sign1,sign2;
char rtmp[NUMBERMAX+2],*rptr;
/* get the signs of the arguments */
sign1 = getsign(&arg1);
sign2 = getsign(&arg2);
/* compute the result */
if (sign1 == sign2) {
signr = sign1;
add(rtmp,arg1,arg2);
}
else
switch (compare(arg1,arg2)) {
case -1:
signr = sign2;
sub(rtmp,arg2,arg1);
break;
case 0:
strcpy(result,"0");
return;
case 1:
signr = sign1;
sub(rtmp,arg1,arg2);
break;
}
/* insert the sign */
if (signr == -1)
strcpy(result,"-");
else
result[0] = EOS;
/* eliminate possible leading zeros */
for (rptr = rtmp; *rptr == '0'; rptr++)
;
/* copy the result */
if (*rptr != EOS)
strcat(result,rptr);
else
strcat(result,"0");
}
/* db_sub - subtract two signed numeric strings */
db_sub(result,arg1,arg2)
char *result,*arg1,*arg2;
{
int signr,sign1,sign2;
char rtmp[NUMBERMAX+2],*rptr;
/* get the signs of the arguments */
sign1 = getsign(&arg1);
sign2 = getsign(&arg2);
/* invert the sign of arg2 */
sign2 = -sign2;
/* compute the result */
if (sign1 == sign2) {
signr = sign1;
add(rtmp,arg1,arg2);
}
else
switch (compare(arg1,arg2)) {
case -1:
signr = sign2;
sub(rtmp,arg2,arg1);
break;
case 0:
strcpy(result,"0");
return;
case 1:
signr = sign1;
sub(rtmp,arg1,arg2);
break;
}
/* insert the sign */
if (signr == -1)
strcpy(result,"-");
else
result[0] = EOS;
/* eliminate a possible leading zero */
for (rptr = rtmp; *rptr == '0'; rptr++)
;
/* copy the result */
if (*rptr != EOS)
strcat(result,rptr);
else
strcat(result,"0");
}
/* add - add two unsigned numeric strings */
static add(result,arg1,arg2)
char *result,*arg1,*arg2;
{
char *vr,*v1,*v2,*vx;
int carry,i,nmin,nmax,nd1,nd2;
/* get number of digits in each argument */
nd1 = getlen(arg1);
nd2 = getlen(arg2);
/* compute the address of the last digit + 1 */
v1 = arg1 + nd1;
v2 = arg2 + nd2;
/* compute minimum and maximum of nd1 and nd2 */
if (nd1 < nd2) {
nmin = -nd1;
nmax = -nd2;
vx = v2;
}
else {
nmin = -nd2;
nmax = -nd1;
vx = v1;
}
/* compute the address of the last result digit + 1 */
vr = result - nmax; vr[0] = EOS;
/* initialize the carry */
carry = 0;
/* add the digits */
for (i = -1; i >= nmin; i--) {
/* check for decimal point */
if (v1[i] == '.')
vr[i] = '.';
else {
/* add the current pair of digits with the carry */
vr[i] = v1[i] + v2[i] + carry - '0';
/* check for carry */
if (vr[i] > '9') {
vr[i] -= 10;
carry = 1;
}
else
carry = 0;
}
}
/* add the remaining digits */
for (; i >= nmax; i--) {
/* add the current digit with the carry */
vr[i] = vx[i] + carry;
/* check for carry */
if (vr[i] > '9') {
vr[i] -= 10;
carry = 1;
}
else
carry = 0;
}
/* check for a carry out and shift digits if necessary */
if (carry == 1) {
/* shift the digits */
for (i = -nmax; i >= 0; i--)
result[i+1] = result[i];
result[0] = '1';
}
}
/* sub - subtract two unsigned numeric strings */
static sub(result,arg1,arg2)
char *result,*arg1,*arg2;
{
char *vr,*v1,*v2,*vx;
int borrow,i,nmin,nmax,nd1,nd2;
/* get number of digits in each argument */
nd1 = getlen(arg1);
nd2 = getlen(arg2);
/* compute the address of the last digit + 1 */
v1 = arg1 + nd1;
v2 = arg2 + nd2;
/* compute minimum and maximum of nd1 and nd2 */
if (nd1 < nd2) {
nmin = -nd1;
nmax = -nd2;
vx = v2;
}
else {
nmin = -nd2;
nmax = -nd1;
vx = v1;
}
/* compute the address of the last result digit + 1 */
vr = result - nmax; vr[0] = EOS;
/* initialize the borrow */
borrow = 0;
/* subtract the digits */
for (i = -1; i >= nmin; i--) {
/* check for decimal point */
if (v1[i] == '.')
vr[i] = '.';
else {
/* subtract the current pair of digits with the borrow */
vr[i] = v1[i] - v2[i] - borrow + '0';
/* check for borrow */
if (vr[i] < '0') {
vr[i] += 10;
borrow = 1;
}
else
borrow = 0;
}
}
/* subtract the remaining digits */
for (; i >= nmax; i--) {
/* subtract the current digit with the borrow */
vr[i] = vx[i] - borrow;
/* check for borrow */
if (vr[i] < '0') {
vr[i] += 10;
borrow = 1;
}
else
borrow = 0;
}
}
/* getsign - get the sign of a numeric string */
static int getsign(parg)
char **parg;
{
int sign;
char *p;
/* eliminate leading spaces */
while (isspace(**parg))
*parg += 1;
/* get the sign */
switch (**parg) {
case '+': *parg += 1;
sign = 1;
break;
case '-': *parg += 1;
sign = -1;
break;
default: sign = 1;
break;
}
/* eliminate leading spaces and zeros */
while (isspace(**parg) || **parg == '0')
*parg += 1;
/* if the value is zero, make sure that the sign is positive */
switch (**parg) {
case EOS: sign = 1;
break;
case '.': for (p = *parg + 1; *p == '0'; p++)
;
if (*p == EOS)
sign = 1;
break;
}
/* return the sign */
return (sign);
}
/* getlen - get the length of a numeric string */
static int getlen(arg)
char *arg;
{
int len;
/* get the length of the string */
len = strlen(arg);
/* eliminate trailing spaces */
while (isspace(arg[len-1]))
len -= 1;
/* return the length */
return (len);
}
/* compare - compare two unsigned numeric strings */
static int compare(arg1,arg2)
char *arg1,*arg2;
{
int len1,len2;
/* compare lengths */
if ((len1 = getlen(arg1)) != (len2 = getlen(arg2)))
if (len1 < len2)
return (-1);
else
return (1);
/* compare strings */
return (strcmp(arg1,arg2));
}

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