PostTwiceDaily2 02/01/2010 (p.m.)

• base conversion in C - CodeCall Programming Forum

  tags: no_tag

  • I just made a function, only using integers for representation. It's able to convert from decimal to Base-(2...9) Base-11 and up is not supported, because it's requires special signs, and not only digits. Here you're...
    
    

    
    

    Code:

    
    

    // The function
    //   First parameter:  The base to convert to
    //   Second parameter: The number to be converted
    int GetBase(int iBase, int iNumber)
    {
    	if(iBase < 2 || iBase > 10)
    		return 0;
    
    	int iResult = iNumber % iBase;
    	int iMultiplier = 10;
    	
    	while((iNumber /= iBase) > 0)
    	{	
    		iResult = (iNumber % iBase) * iMultiplier + iResult;
    		iMultiplier *= 10;
    	}
    
    	return iResult;
    }

    
    

    
    

    Code:

    
    

    // A test, to see how it works
    int i;
    for(i = 2; i < 10; i++)
    	printf("123 in Base-%d: %d\n", i, GetBase(i, 123));

    
    

    
    

    Code:

    
    

    // Sample run
    
    123 in Base-2: 1111011
    123 in Base-3: 11120
    123 in Base-4: 1323
    123 in Base-5: 443
    123 in Base-6: 323
    123 in Base-7: 234
    123 in Base-8: 173
    123 in Base-9: 146

    
    

    
    

    
    
    
    
    
    
    
    
    
    
    
    
    
    

    
    
    

• Base Conversion with 3 inputs - C

  tags: no_tag

  • int convert(const char *text, int inbase, int outbase);

    int convert(const char *text, int inbase, int outbase);
    Pass the function the text "43" as is. Convert the "8" and the "10" to ints however you choose -- maybe even your own atoi!
    
    
    
    The convert function then does two things:
    1. It breaks down the incoming text into an integer value using the inbase.
    2. It creates an output string based on the outbase.
    
    
    The first part involves a loop in which you multiply the current integer value by inbase and then add the "digit" value. Note that the text conversion (for the digit value) from '4' to 4 is easy, but for bases higher than 10 it is a little extra work.
    
    
    
    The second part involves div and mod operations to create the digits in outbase. Depending on how you do this, it might be easier to create this string "backwards" and then reverse it.
    
    
    
    I hope I have mentioned enough of the basic elements to give you some sort of starting point to begin writing your coding attempt.

• Number base conversion - Rosetta Code

  tags: no_tag

  • C

    
    

    #include <stdlib.h>
    #include <string.h>
    #include <assert.h>
     
    #define MAX_OUTSTR_LEN 65
    char *to_base(long num, int base)
    {
      static const char *map = "0123456789abcdefghijklmnopqrstuvwxyz";
      char *result = NULL;
      int i=0, j;
      char t;
     
      if ( base > strlen(map) ) return NULL;
     
      result = malloc(sizeof(char)*MAX_OUTSTR_LEN);
      *result = 0;
      do {
        result[i++] = map[ num%base ];
        num /= base;
      } while(num != 0);
      result[i] = 0;
      for(j=0; j < i/2; j++) { /* invert the rests */
        t = result[j];
        result[j] = result[i-j-1];
        result[i-j-1] = t;
      }
      return result;
    }
     
    long from_base(const char *num_str, int base)
    {
      char *endptr;
      int result = strtol(num_str, &endptr, base);
      assert(*endptr == '\0'); /* if there are any characters left, then string contained invalid characters */
      return result;
      /* there is also strtoul() for parsing into an unsigned long */
      /* in C99, there is also strtoll() and strtoull() for parsing into long long and unsigned long long, respectively */
    }

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