Programming

formatNum(1123.45,3,8) = "   1,123.450"
formatNum(1123.45,2,8) = "   1,123.45"
formatNum(1123.45,1,8) = "   1,123.4" (truncation rather than rounding)

                   1
                   1.10
                   1.11
                 111.11
               1,111
           1,111,111.10

#include <stdlib.h>
#include <stdio.h>
char *formatNum(double num, int dec, int pad)
{
  char* OutStr;
  sprintf(OutStr,"%f",num);
  return OutStr;
}

#include <stdio.h>
#include <string.h>

void formatNum(char *buf, double n, int decimals, int pad)
{
        char cmdstr[64]; // Holds a command string for sprintf
        sprintf(cmdstr, "%%.%df", decimals); // Create a format string like %.3f
        memset(buf, ' ', pad); // Fill padding area with spaces
        sprintf(buf+pad, cmdstr, n);        // Print after spaces
}

int main(void)
{
        char buf[128]; // sprintf needs a buffer, not just a pointer.
        formatNum(buf, 3.14159, 3, 8);
        printf("Result was:  '%s'\n", buf);
}

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
void subString(const char *source, int begin, int end, char *destination) {
 int i = 0;
 while ( begin <= end ) {
  destination[i++] = source[begin++];
 }
}
char *commaInt(unsigned long n)
{
 static int comma = ',';
 static char retbuf[30];
 char *p = &retbuf[sizeof(retbuf)-1];
 int i = 0;
 *p = '\0';
 do {
  if(i%3 == 0 && i != 0)
  *--p = comma;
  *--p = '0' + n % 10;
  n /= 10;
  i++;
 } while(n != 0);
 return p;
}
char *commaStr(char* inStr, int decimals, int padto)
{
 double inDbl = atof(inStr);
 
 char cmdstr[64];
 static char retbuf[256];
 char *out = &retbuf[sizeof(retbuf)-1];
 long intpart = (long)inDbl;
 char* front = commaInt(intpart);
 char* intpartStr;
 sprintf(intpartStr,"%ld",intpart);
 int intpartLen = strlen(intpartStr);
 char decSubstr[80];
 memset(decSubstr, 0L, sizeof(decSubstr));
 subString(inStr, intpartLen, intpartLen + decimals, decSubstr);
 printf("DecSubstr: %s\n", decSubstr);
 sprintf(cmdstr, "%%%ds%%s\n", padto, decimals); // Create a format string like %10s%s
 sprintf(retbuf, cmdstr, front, decSubstr);
 
 out=retbuf;
 return out;
}
int main() {
 char* inStr;
 char* fmtStr;
 inStr = "923456712345678.1234";
 fmtStr = commaStr(inStr,3,25);
 printf("Formatted: %s", fmtStr);
 inStr = "456712345678.123456";
 fmtStr = commaStr(inStr,3,25);
 printf("Formatted: %s", fmtStr);
 inStr = "923456712345678.1";
 fmtStr = commaStr(inStr,3,25);
 printf("Formatted: %s", fmtStr);
 inStr = "923456712345678.1";
 fmtStr = commaStr(inStr,1,25);
 printf("Formatted: %s", fmtStr);
}